Nature of _the scene_ was such that one would do an effect and then another would wonder how it was done and try to better it, all without source. That's kind of why it's rare for you to find sources of such things.
Either to protect the authors of the original software to check if the warez group got the full algorithm or if they have something mildly different from the original that allows the authors to detect a keygen in newer versions, or because the warez group wants to make life more difficult for copycats... or, and I've seen my fair share of that (and earned good money to clean up), a third party wrapped a highly popular keygen like for Adobe CS6 in some sort of malware and wanted to avoid detection.
You can find a lot of groups/individuals publish a lot of esp. their older stuff now.
Two off the top of my head:
- https://github.com/ConspiracyHu (and they made a W32 port of Future Crew's Second Reality, which is public domain: https://github.com/mtuomi/SecondReality)
- Farbrausch published their original demo tool source ages ago: https://github.com/farbrausch/fr_public
I see EXE names and I think cracks were distributed that way. I don’t have enough insight into the cracking scene to know if there was any underground open source back then.
These days, having the source to these graphic effects would be invaluable!