Looks like some interesting work is being done here, though there is also a pre-compiled executable included.
One thing i completely forgot about is that the PC port of the game was initially
only on DOS, not Windows. So the fact this is a native Windows build is unusual.
In terms of branches, "WIN95" appears to be a build solely designed for
ATI Rage GPUs. While "Wipeout 98" was designed for the GPU agnostic Direct3d API.
Edit: I dug around, and it looks like the ATI Rage version did receive an
extremely limited print run in a few bundles. I suspect mainly for the GPU itself. But the closest evidence i could find was it being included in
a series of Japanese PCs manufactured by a company known as
"Apricot".
The Direct3D build is still completely new, it looks like.
It seems like the release had nothing to do with the original developers, meaning that It may have been stolen.
Not really "stolen" specifically, the more likely explanation is that Forest of Illusion acquired a HDD or disk containing the source from a former Psygnosis dev.