We can still update directly through the site, but yeah, we all kind of just lost interest in this. Maybe you'd like to take over?

I might suggest holding off until DJazz gets the collaboration-enabled WebJCS ready for primetime. Using that should speed up your work considerably, and given your current rate of production, it's not as if you'd be making any great sacrifice by waiting.

Good idea, but I would rather not install a Chrome-based browser. I have my reasons, not going to spread them here.

If it actually is good, then I might start a client at a webserver to 'host' the level so that others might join in.

Did you try it in latest Firefox or Safari? Seems like most work, except saving. I still recommend Chrome for the performance and speed.
I have not released WebJCS with collab and FF fixes yet, but you can try it here: http://djazz.mine.nu:8010/