(Disclosure: I work for Vodafone Group Services - but I think this is a great idea regardless)
From poking around the site, it appears it's a collaboration space for mobile application developers, testers, and anyone interested in mobile communications. What I'm particularly intrigued (and keen to see how it develops) is the mobile art space.
Application developers can also create project spaces, to enable collaboration on mobile communications projects. So, there are spaces for files, blogging, user forums, private project-only spaces. Of course, Vodafone reserve some rights, so make sure you're happy with the rules on applications and IPR before you upload - as you should with pretty much anything you do - check the T's & C's. The developer space doesn't appear to be a traditional software development space (like a sourceforge, or a rubyforge), but more like a file sharing space and promotion space. I can't confirm this, because I have haven't got a project space yet. Maybe I'll develop a little something with mojax, and see if I can get it hosted at Betavine.
What's also interesting if you're a young fella (or fell'ess) is that Vodafone are looking to run competitions, and offer internships and externships. So, get in while the gettings good I say. I'd have liked to have this sort of thing around when I was at uni... There are some competitions there now with some healthy looking prizes (â‚¬5000 for 1st - awarded to your uni to be shared with you) so check it out.
Anyway, I am very pleased that finally, the company I work for has taken this sort of initiative. I personally would have liked to see it done earlier, like, when the first round of handsets came out with development environments. However, software development on handsets has traditionally been complex, time consuming and painful. BUT, with the emergence of J2ME, and more recently AJAX frameworks for handsets it's becoming a relatively trivial activity. I doubt the concept would have worked before, but I feel now the time is right.