I can't imagine textbook XP or RUP working effectively for something like this. The Mozilla Project is historical from a software engineer's point of view. With the recent surge Linux has seen in the PC operating systems market, open-source development is more prevalent than ever. Many people will be keeping a close eye on Netscape, seeing if their new communications suite delivers on its promises. And if it does, maybe we'll see companies make the daring step from proprietary software to a more open and free market.
Any comments are of course welcome.
Quite a lot is being written about open source projects and how they are managed. Eric Raymond's The Cathedral and the Bazaar is one of the most well known, and perhaps the best. Start with it.