Court proceedings are a great source in the very special niche of early games. Thanks to multiple lawsuites regarding Bally, Magnavox, Sega, etc, where about everybody appeared at least once as an expert witness and left some source codes as a witness deposit.
E.g., a few weeks ago, I retyped and assembled a listing for SpaceWar for the LINC (by A.J. Hance, 1965) from the Hagley Museum:
https://www.masswerk.at/spacewar/linc/source/LINC-SpaceWar-AJH1965-listing.txt
https://www.masswerk.at/spacewar/linc/source/LINC-SpaceWar-AJH1965-description.txt
(The source had been once distributed by DECUS, and I think, the description probably went with this.)
Now I’m writing a LINC emulator…