He refers to Vim9 script in the comment about the lack of work on it on the top of the page, so apparently it saw work fairly recently. To my surprise, I thought it was long dead.

I still can't get past the unpaired } as the ending delimiter. It's a superficial reason, but there are many languages out there, and it's easy to be picky.

I found a fork of it on GitHub for those interested. Here's a link to the first commit which hopefully contains unmodified import of Moolenaar's hg repository: https://github.com/TsukiGva2/unnoficial-zimbu/tree/3ea616b33...

From a 2021 mailing list post:

Yes, bitbucket has dropped Mercurial. I'll look into putting Zimbu up on github. I'm not currently working on it, but some people might find it interesting and want to try it out.

Nothing on his GitHub profile either, just a mention of Zimbu in his bio: https://github.com/brammool?tab=repositories