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From the audio-sourcing-sweep (45 sources verified). The load-bearing test — can a paid SaaS render the audio into customers' MP4s AND vendor the file — rules out almost all "royalty-free" libraries; only CC0/PD passes cleanly. - USE (CC0, vendorable): FreePD (music; site dead → archive.org/details/freepd), Kenney.nl (SFX; the one clean-from-Iran source), Freesound-CC0, OpenGameArt-CC0. - CAUTION: incompetech CC-BY (needs attribution pipeline), aggregators (verify per-track), Sonniss/Pixabay (render-input-only, never vendor raw). - AVOID/reference-only: Mixkit/Uppbeat/Bensound/Envato/Zapsplat/… (clauses + OFAC). - Persian = no clean CC0 bulk source → commission + self-CC0 long-term. Real files need a VPN/non-Iran fetch (acquire-once-then-vendor makes the licence perpetual); only the 4 self-authored ffmpeg stubs are vendored today. Firewall rules mirror the illustration assets.json + check-assets guard (already scans audio). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>