That is, unfortunately correct.
There’s an alpha7 you can download from the Github page (click the big downloads button): https://github.com/Mark-H/Versionx
that sort of is more compatible, but that’s more a hack job than anything else... this is one of those ambitious projects that start of great, but lack proper planning ahead of time to make sure it can run stable and, simply said, doesn’t break on new releases. Really not a project of mine that I’m proud of..
I’m hoping that somewhere over the next weeks I have some time to get started on a new addon that will take the functionality VersionX offers and then some more. More configurable, hopefully an import script to import history from VersionX and flexible in such a way that it definitely wont break again. (at least until 3.0)
I do know that someone else has been trying to get VersionX running in 2.1 and got quite far with that..