There were some forks and merges already back then that probably did not help. Then Canoncial hired the main dev, with the main project not surviving far beyond his later departure. Official end point for the project seems to have been https://www.phoronix.com/news/MTI2ODU, in 2012 and mentioning Wayland as reason (as if that were anywhere close back then).

But actually, the launchpad repo has recent commits (or do I read https://code.launchpad.net/~compiz-team/compiz/+git/compiz/+... wrong), and so does https://github.com/compiz-reloaded. You can still just use one of those if you want - Void Linux for example has it packaged, and so does Ubuntu.