I have considered hosting an instance but my ISP has vague terms prohibiting that sort of thing.

Have you had any issues with your ISP?

As far as I know email is an entirely different protocol than the fediverse so they wouldn’t coincide. It’s possible someone hosts an email server alongside their fediverse server but that’s not really the same thing as it being part of the fediverse.

There’s perforce which is primarily used for game development. Often games have a lot of binary files that are hard/impossible to generate diffs of unlike text based files. Perforce requires you to check out individual files and prevents any merge conflicts on an individual file basis.

Make that two