diff --git a/scripts/license_checker.py b/scripts/license_checker.py
new file mode 100644
index 0000000..16d4c0d
--- /dev/null
+++ b/scripts/license_checker.py
@@ -0,0 +1,506 @@
+#!/usr/bin/env python3
+"""
+License Checker — Pipeline 5.4
+Scans dependency files for a project, resolves license info, flags incompatibilities.
+
+Acceptance:
+  [x] Reads license for each dep
+  [x] Flags: GPL in MIT project, unknown licenses
+  [x] Output: license compatibility report
+
+Usage:
+    python3 license_checker.py <project_dir> [--project-license MIT] [--format json|text]
+    python3 license_checker.py <project_dir> --scan-deps
+"""
+
+import argparse
+import json
+import os
+import re
+import subprocess
+import sys
+import urllib.request
+import urllib.error
+from dataclasses import dataclass, field, asdict
+from enum import Enum
+from pathlib import Path
+from typing import Optional
+
+
+class Severity(Enum):
+    OK = "ok"
+    WARNING = "warning"
+    ERROR = "error"
+    UNKNOWN = "unknown"
+
+
+# SPDX license compatibility matrix
+# Key: (dependency_license, project_license) -> compatible?
+# Copyleft licenses are NOT compatible with permissive projects
+COPYLEFT_FAMILIES = {
+    "GPL-2.0", "GPL-2.0-only", "GPL-2.0-or-later",
+    "GPL-3.0", "GPL-3.0-only", "GPL-3.0-or-later",
+    "AGPL-3.0", "AGPL-3.0-only", "AGPL-3.0-or-later",
+    "LGPL-2.0", "LGPL-2.1", "LGPL-3.0",
+    "LGPL-2.0-only", "LGPL-2.1-only", "LGPL-3.0-only",
+    "LGPL-2.0-or-later", "LGPL-2.1-or-later", "LGPL-3.0-or-later",
+    "MPL-2.0",  # Weak copyleft — file-level
+    "EUPL-1.1", "EUPL-1.2",
+    "OSL-3.0",
+    "SSPL-1.0",
+    "CC-BY-SA-4.0", "CC-BY-SA-3.0",
+    "CC-BY-NC-4.0", "CC-BY-NC-3.0",
+}
+
+PERMISSIVE_LICENSES = {
+    "MIT", "BSD-2-Clause", "BSD-3-Clause", "Apache-2.0",
+    "ISC", "Unlicense", "CC0-1.0", "0BSD", "BSL-1.0",
+    "Zlib", "PSF-2.0", "Python-2.0",
+}
+
+# Common aliases
+LICENSE_ALIASES = {
+    "mit": "MIT",
+    "bsd": "BSD-3-Clause",
+    "bsd-2": "BSD-2-Clause",
+    "bsd-3": "BSD-3-Clause",
+    "bsd license": "BSD-3-Clause",
+    "apache": "Apache-2.0",
+    "apache 2.0": "Apache-2.0",
+    "apache-2.0": "Apache-2.0",
+    "apache software license": "Apache-2.0",
+    "apache software license 2.0": "Apache-2.0",
+    "gpl": "GPL-3.0",
+    "gpl-2": "GPL-2.0",
+    "gpl-3": "GPL-3.0",
+    "gplv2": "GPL-2.0",
+    "gplv3": "GPL-3.0",
+    "gnu general public license": "GPL-3.0",
+    "gnu general public license v3": "GPL-3.0",
+    "gnu general public license v2": "GPL-2.0",
+    "gnu lesser general public license v2": "LGPL-2.1",
+    "gnu lesser general public license v3": "LGPL-3.0",
+    "lgpl": "LGPL-3.0",
+    "lgpl-2.1": "LGPL-2.1",
+    "lgpl-3": "LGPL-3.0",
+    "agpl": "AGPL-3.0",
+    "agpl-3.0": "AGPL-3.0",
+    "agplv3": "AGPL-3.0",
+    "isc": "ISC",
+    "mpl": "MPL-2.0",
+    "mpl-2.0": "MPL-2.0",
+    "mozilla public license 2.0": "MPL-2.0",
+    "unlicense": "Unlicense",
+    "public domain": "Unlicense",
+    "cc0": "CC0-1.0",
+    "cc0-1.0": "CC0-1.0",
+    "psf": "PSF-2.0",
+    "python software foundation license": "PSF-2.0",
+    "the mit license": "MIT",
+    "mit license": "MIT",
+}
+
+
+@dataclass
+class DepLicense:
+    name: str
+    version: str = ""
+    license: str = "UNKNOWN"
+    source: str = ""  # where we found the dep (requirements.txt, package.json, etc.)
+    severity: Severity = Severity.UNKNOWN
+    message: str = ""
+
+
+@dataclass
+class LicenseReport:
+    project_dir: str
+    project_license: str = "MIT"
+    dependencies: list = field(default_factory=list)
+    summary: dict = field(default_factory=dict)
+    errors: list = field(default_factory=list)
+    warnings: list = field(default_factory=list)
+
+
+def normalize_license(raw: str) -> str:
+    """Normalize a license string to SPDX identifier."""
+    if not raw or raw.strip() in ("UNKNOWN", "UNKNOWN:", ""):
+        return "UNKNOWN"
+    cleaned = raw.strip().lower()
+    # Remove version specifiers like "MIT License (MIT)"
+    cleaned = re.sub(r"\(.*?\)", "", cleaned).strip()
+    cleaned = re.sub(r"\s+license$", "", cleaned).strip()
+    cleaned = re.sub(r"^the\s+", "", cleaned).strip()
+    if cleaned in LICENSE_ALIASES:
+        return LICENSE_ALIASES[cleaned]
+    # Check if it already looks like SPDX
+    upper = raw.strip()
+    if upper in COPYLEFT_FAMILIES or upper in PERMISSIVE_LICENSES:
+        return upper
+    return raw.strip()
+
+
+def check_compatibility(dep_license: str, project_license: str) -> tuple[Severity, str]:
+    """Check if a dependency license is compatible with the project license."""
+    if dep_license == "UNKNOWN":
+        return Severity.WARNING, "License unknown — manual review needed"
+    
+    if dep_license in PERMISSIVE_LICENSES:
+        return Severity.OK, "Compatible (permissive)"
+    
+    if dep_license in COPYLEFT_FAMILIES:
+        # Copyleft in a permissive project is a problem
+        if project_license in PERMISSIVE_LICENSES:
+            return Severity.ERROR, f"Copyleft ({dep_license}) in permissive ({project_license}) project"
+        # Copyleft in same family is OK
+        if dep_license.startswith(project_license.split("-")[0]):
+            return Severity.OK, "Compatible (same copyleft family)"
+        return Severity.WARNING, f"Review needed: {dep_license} with {project_license}"
+    
+    return Severity.UNKNOWN, f"Unrecognized license: {dep_license}"
+
+
+def parse_requirements_txt(path: str) -> list[DepLicense]:
+    """Parse requirements.txt format."""
+    deps = []
+    with open(path) as f:
+        for line in f:
+            line = line.strip()
+            if not line or line.startswith("#") or line.startswith("-"):
+                continue
+            # Parse name==version or name>=version etc.
+            match = re.match(r"^([a-zA-Z0-9_.-]+)(?:[>=<!~].*)?$", line)
+            if match:
+                deps.append(DepLicense(name=match.group(1), source="requirements.txt"))
+    return deps
+
+
+def parse_pyproject_toml(path: str) -> list[DepLicense]:
+    """Parse pyproject.toml dependencies."""
+    deps = []
+    try:
+        # Use tomllib (Python 3.11+) or fall back to regex
+        import tomllib
+        with open(path, "rb") as f:
+            data = tomllib.load(f)
+    except ImportError:
+        # Fallback: regex parse
+        with open(path) as f:
+            content = f.read()
+        # Find [project.dependencies] section
+        match = re.search(r"\[project\]\s*dependencies\s*=\s*\[(.*?)\]", content, re.DOTALL)
+        if match:
+            for dep_str in re.findall(r'"([^"]+)"', match.group(1)):
+                name = re.match(r"^([a-zA-Z0-9_.-]+)", dep_str)
+                if name:
+                    deps.append(DepLicense(name=name.group(1), source="pyproject.toml"))
+        return deps
+
+    project_deps = data.get("project", {}).get("dependencies", [])
+    for dep_str in project_deps:
+        name = re.match(r"^([a-zA-Z0-9_.-]+)", dep_str)
+        if name:
+            deps.append(DepLicense(name=name.group(1), source="pyproject.toml"))
+    return deps
+
+
+def parse_package_json(path: str) -> list[DepLicense]:
+    """Parse package.json dependencies."""
+    deps = []
+    with open(path) as f:
+        data = json.load(f)
+    for section in ("dependencies", "devDependencies"):
+        for name, version in data.get(section, {}).items():
+            deps.append(DepLicense(name=name, version=version, source="package.json"))
+    return deps
+
+
+def parse_cargo_toml(path: str) -> list[DepLicense]:
+    """Parse Cargo.toml dependencies (basic)."""
+    deps = []
+    with open(path) as f:
+        for line in f:
+            match = re.match(r'^([a-zA-Z0-9_-]+)\s*=\s*"', line.strip())
+            if match and line.strip()[0] != "[" and line.strip() != "[dependencies]":
+                deps.append(DepLicense(name=match.group(1), source="Cargo.toml"))
+    return deps
+
+
+def parse_go_mod(path: str) -> list[DepLicense]:
+    """Parse go.mod dependencies."""
+    deps = []
+    with open(path) as f:
+        in_require = False
+        for line in f:
+            line = line.strip()
+            if line == "require (":
+                in_require = True
+                continue
+            if line == ")" and in_require:
+                in_require = False
+                continue
+            if in_require:
+                parts = line.split()
+                if len(parts) >= 2:
+                    deps.append(DepLicense(name=parts[0], version=parts[1], source="go.mod"))
+    return deps
+
+
+def scan_dep_files(project_dir: str) -> list[DepLicense]:
+    """Find and parse all dependency files in a project."""
+    all_deps = []
+    parsers = {
+        "requirements.txt": parse_requirements_txt,
+        "requirements-dev.txt": parse_requirements_txt,
+        "requirements_prod.txt": parse_requirements_txt,
+        "pyproject.toml": parse_pyproject_toml,
+        "setup.py": None,  # TODO: parse setup.py
+        "package.json": parse_package_json,
+        "Cargo.toml": parse_cargo_toml,
+        "go.mod": parse_go_mod,
+    }
+    
+    for filename, parser in parsers.items():
+        path = os.path.join(project_dir, filename)
+        if os.path.exists(path) and parser:
+            try:
+                deps = parser(path)
+                all_deps.extend(deps)
+            except Exception as e:
+                print(f"Warning: Failed to parse {filename}: {e}", file=sys.stderr)
+    
+    # Also check subdirectories for monorepos (one level deep)
+    for entry in os.listdir(project_dir):
+        subdir = os.path.join(project_dir, entry)
+        if os.path.isdir(subdir) and not entry.startswith("."):
+            for filename, parser in parsers.items():
+                path = os.path.join(subdir, filename)
+                if os.path.exists(path) and parser:
+                    try:
+                        deps = parser(path)
+                        for d in deps:
+                            d.source = f"{entry}/{filename}"
+                        all_deps.extend(deps)
+                    except Exception:
+                        pass
+    
+    return all_deps
+
+
+def lookup_pypi_license(package_name: str) -> str:
+    """Look up license from PyPI API."""
+    try:
+        url = f"https://pypi.org/pypi/{package_name}/json"
+        req = urllib.request.Request(url, headers={"Accept": "application/json"})
+        resp = urllib.request.urlopen(req, timeout=10)
+        data = json.loads(resp.read())
+        # Try classifiers first
+        for classifier in data.get("info", {}).get("classifiers", []):
+            if classifier.startswith("License ::"):
+                parts = classifier.split(" :: ")
+                if len(parts) >= 3:
+                    return parts[-1]
+        # Fall back to license field
+        lic = data.get("info", {}).get("license", "")
+        if lic and len(lic) < 100:
+            return lic
+        # Try license_expression
+        le = data.get("info", {}).get("license_expression", "")
+        if le:
+            return le
+        return "UNKNOWN"
+    except Exception:
+        return "UNKNOWN"
+
+
+def lookup_npm_license(package_name: str) -> str:
+    """Look up license from npm registry."""
+    try:
+        url = f"https://registry.npmjs.org/{package_name}"
+        req = urllib.request.Request(url, headers={"Accept": "application/json"})
+        resp = urllib.request.urlopen(req, timeout=10)
+        data = json.loads(resp.read())
+        lic = data.get("license", "UNKNOWN")
+        if isinstance(lic, dict):
+            lic = lic.get("type", "UNKNOWN")
+        return lic or "UNKNOWN"
+    except Exception:
+        return "UNKNOWN"
+
+
+def detect_project_license(project_dir: str) -> str:
+    """Detect the project's own license."""
+    for name in ("LICENSE", "LICENSE.md", "LICENSE.txt", "LICENCE", "COPYING"):
+        path = os.path.join(project_dir, name)
+        if os.path.exists(path):
+            with open(path) as f:
+                content = f.read().upper()
+            if "MIT LICENSE" in content or "MIT" in content[:200]:
+                return "MIT"
+            if "APACHE" in content and "2.0" in content:
+                return "Apache-2.0"
+            if "GNU GENERAL PUBLIC LICENSE" in content:
+                if "VERSION 3" in content:
+                    return "GPL-3.0"
+                if "VERSION 2" in content:
+                    return "GPL-2.0"
+            if "BSD" in content[:500]:
+                if "3-CLAUSE" in content or "THREE CLAUSE" in content:
+                    return "BSD-3-Clause"
+                return "BSD-2-Clause"
+            if "ISC" in content[:200]:
+                return "ISC"
+    # Check pyproject.toml
+    pypath = os.path.join(project_dir, "pyproject.toml")
+    if os.path.exists(pypath):
+        with open(pypath) as f:
+            content = f.read()
+        match = re.search(r'license\s*=\s*\{\s*text\s*=\s*"([^"]+)"', content)
+        if match:
+            return normalize_license(match.group(1))
+        match = re.search(r'license\s*=\s*"([^"]+)"', content)
+        if match:
+            return normalize_license(match.group(1))
+    return "UNKNOWN"
+
+
+def resolve_licenses(deps: list[DepLicense], cache: dict = None) -> None:
+    """Resolve license info for all dependencies."""
+    if cache is None:
+        cache = {}
+    
+    for dep in deps:
+        if dep.name in cache:
+            dep.license = cache[dep.name]
+            continue
+        
+        # Determine ecosystem
+        if dep.source in ("package.json",):
+            raw = lookup_npm_license(dep.name)
+        else:
+            raw = lookup_pypi_license(dep.name)
+        
+        dep.license = normalize_license(raw)
+        cache[dep.name] = dep.license
+
+
+def generate_report(deps: list[DepLicense], project_license: str) -> LicenseReport:
+    """Generate the compatibility report."""
+    report = LicenseReport(
+        project_dir="",
+        project_license=project_license,
+        dependencies=[],
+    )
+    
+    counts = {"ok": 0, "warning": 0, "error": 0, "unknown": 0}
+    
+    for dep in deps:
+        severity, message = check_compatibility(dep.license, project_license)
+        dep.severity = severity
+        dep.message = message
+        counts[severity.value] += 1
+        
+        if severity == Severity.ERROR:
+            report.errors.append(f"{dep.name}: {message}")
+        elif severity == Severity.WARNING:
+            report.warnings.append(f"{dep.name}: {message}")
+        
+        report.dependencies.append(asdict(dep))
+    
+    report.summary = {
+        "total": len(deps),
+        **counts,
+        "project_license": project_license,
+    }
+    
+    return report
+
+
+def format_text(report: LicenseReport) -> str:
+    """Format report as human-readable text."""
+    lines = []
+    lines.append("=" * 60)
+    lines.append("  LICENSE COMPATIBILITY REPORT")
+    lines.append("=" * 60)
+    lines.append(f"  Project License: {report.project_license}")
+    lines.append(f"  Dependencies: {report.summary.get('total', 0)}")
+    lines.append(f"  OK: {report.summary.get('ok', 0)}  "
+                 f"WARN: {report.summary.get('warning', 0)}  "
+                 f"ERR: {report.summary.get('error', 0)}  "
+                 f"UNK: {report.summary.get('unknown', 0)}")
+    lines.append("-" * 60)
+    
+    for dep in report.dependencies:
+        icon = {"ok": "[OK]", "warning": "[!!]", "error": "[XX]", "unknown": "[??]"}
+        sev = dep.get("severity", "unknown")
+        name = dep.get("name", "?")
+        lic = dep.get("license", "?")
+        msg = dep.get("message", "")
+        lines.append(f"  {icon.get(sev, '[ ]')} {name:30s} {lic:20s} {msg}")
+    
+    if report.errors:
+        lines.append("-" * 60)
+        lines.append("  ERRORS:")
+        for e in report.errors:
+            lines.append(f"    - {e}")
+    
+    if report.warnings:
+        lines.append("-" * 60)
+        lines.append("  WARNINGS:")
+        for w in report.warnings:
+            lines.append(f"    - {w}")
+    
+    lines.append("=" * 60)
+    return "\n".join(lines)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="License Checker — Pipeline 5.4")
+    parser.add_argument("project_dir", help="Project directory to scan")
+    parser.add_argument("--project-license", default=None,
+                        help="Project license SPDX id (auto-detected if omitted)")
+    parser.add_argument("--format", choices=["json", "text"], default="text",
+                        help="Output format")
+    parser.add_argument("--scan-deps", action="store_true",
+                        help="Only scan and list deps (skip license lookup)")
+    args = parser.parse_args()
+    
+    project_dir = os.path.abspath(args.project_dir)
+    if not os.path.isdir(project_dir):
+        print(f"Error: {project_dir} is not a directory", file=sys.stderr)
+        sys.exit(1)
+    
+    # Detect project license
+    project_license = args.project_license or detect_project_license(project_dir)
+    
+    # Scan deps
+    deps = scan_dep_files(project_dir)
+    if not deps:
+        print(f"No dependencies found in {project_dir}", file=sys.stderr)
+        sys.exit(0)
+    
+    print(f"Found {len(deps)} dependencies", file=sys.stderr)
+    
+    if args.scan_deps:
+        for d in deps:
+            print(f"  {d.name} ({d.source})")
+        sys.exit(0)
+    
+    # Resolve licenses
+    print("Resolving licenses...", file=sys.stderr)
+    resolve_licenses(deps)
+    
+    # Generate report
+    report = generate_report(deps, project_license)
+    report.project_dir = project_dir
+    
+    if args.format == "json":
+        print(json.dumps(asdict(report), indent=2, default=str))
+    else:
+        print(format_text(report))
+    
+    # Exit code: 1 if errors, 0 otherwise
+    sys.exit(1 if report.errors else 0)
+
+
+if __name__ == "__main__":
+    main()