Mooix is a MOO that is implemented on top of unix and which can be programmed online in any language.
I stopped developing mooix around 2001; a few other people made commits from time to time for the next decade, but now it is done.
I have some grandiose plans for the next generation of mooix, which I might get around to fleshing out some day, but probably not.
Some thoughts on mooix in my blog.
Mooix is archived: https://archive.org/details/MooixArchive