[...]allegedly due to potential copyright / license issues.
[...]Even the RTOR.pdf has been taken down.
[...]I do not know what to make of this[...]
Neither do I. As prose was also withdrawn (unlikely for copyright) there seems more to the story.
If it's under something like the GPL, the license, once you have code licensed under it, is irrevocable. You can just post it on github or whatever if someone thinks they can force you to take it down, they'll have to let you know about it. In this way, you can either learn who's causing trouble (probably no one) or make the code available to all again [...]
Exactly; people will want to fork, whether legal in their country or just ones that would host code (some developing countries seem to not care at all, but even Sweden's FTP.SUNet.se hosts PernAngband code, but Pern copyright holders can do nothing... only in countries that follow USA.)
It was taken down because the Interhack code breached copyright of some other code that was included in Interhack many eons ago[...]
The proper Free/Libre/Opensource Software (FLOSS) thing to do would be to state & remove that for another (pre-)alpha release, continue or encourage people to fork. I want to fork it, just maybe don't have the time (but probably someone can eventually.) However, for that to happen, it's best the full (detailed) truth comes out, responsibly: so the potential copyright issue isn't potentially forced on to others.
I wonder if ithe ‘issue’ was rereleasing (Net)Hack code under GPL2 rather than (Net)Hack's license, but maybe derivative works are same license... or (if not and/or you didn't want that, or if doesn't allow other-licensed files as InterHack's GPL2 does,) just all (Net)Hack code would need replacing. If that's not it, maybe the real issue is you don't like FLOSS as much. If so (though I disagree with the practice,) why not have a FLOSS version and a proprietary version with more details/content? (one can dual-license their own code... maybe even under both (Net)Hack's license and GPL) Other major roguelikes do that, like ToME4 (FLOSS and commercial version with the same engine,) and ADOM, though proprietary, has freeware and pay-only versions, along with much other successful commercial & FLOSS software doing similar to ToME4 (having an ‘Opensource’ version and more advanced proprietary version with different license... then ‘Opensource’ programmers improve the ‘Opensource’ version and the company incorporates it into the proprietary version.)
I'm not rich, but a
Free Software Foundation associate member and have donated up to $10 or $20 a time to FLOSS I like. I avoid commercial software/games, though might make exception if a friend played, but would spend less on those, and (from my ethics) I'd feel guilty playtesting anything proprietary or something then I get free but others buy (plus, I couldn't see or try to improve code or report as many bugs.) I'd rather have seen a donations/‘crowdsource’ project to revive InterHack, and/or encouraging people to fork it with copyrighted stuff removed.
I'm very sad to see InterHack end (for now,) as I spent a lot of (wasted) time compiling, trying it, finally making a SlackBuild so people could automatically build & install it in Slackware GNU/Linux (then other OS people copy/use or check SlackBuilds) with its quasi-official package build manager, and waiting years to see if there would be a stable release. I'm still willing to do it if InterHack comes back, but not for a non-FLOSS game (though wouldn't care if game content/world files are copyrighted.)