Due to legal problems, Hydra (the well-received multi-author editing program for OS X) has apparently changed its name to SubEthaEdit. Can't quite place where you've heard that before? It's from Douglas Adams:

The Guide was compiled by researchers roaming round the galaxy, beaming their copy in, which was then instantly available to anybody to read. Over, believe it or not, something called the SubEthaNet. [...] I really didn't foresee the Internet. But then, neither did the computer industry. Not that that tells us very much of course - the computer industry didn't even foresee that the century was going to end. But I did have the inkling of an idea that a collaborative guide, one that was written and kept up to date by the people who used it, in real time, might be a neat idea.

So far as I can tell, it still lacks the one additional feature I'd really like it to have, which is for it to retain information about all the authors even after the collaborative work is over. (However, since it's 8am EDT, it's hard to find someone to test that with...)