Yves Grolet, programmer on Amiga classics such as Agony and Unreal (so not the Epic game!) has recently archived and released remains of his Amiga hard drive and various floppy disks to the public domain.
These include the full sources for Agony and various other prototypes, and bits and pieces. People are free to do whatever they like with the sources, as long as it isn’t for commercial use.
A fantastic treasure trove which you should definitely check out:
Thanks to @AmigaL0ve and Fabrizio Bartoloni for flagging up the release.