I don't care whether you build the software from scratch or just create a bunch of modifications for some already-existing software. There are benefits and drawbacks to both methods which will be considered in relation to the rest of your bid.
Whats wrong with email? I would like to see normal lists. Because of less traffic Mailman would be a good choice. Very easy to set up also. Forums are for little people. It is stupid to have to use something like that. Very susceptible for XSS and other attacks. When I came here I was wondering if you really know what you are doing. Sorry if I have to say it so plainly. I'm surprised that nothing has happened yet.
I would prefer simple mailing lists. So I can read new messages and be simultaneously logged into Mt Gox. On the same machine, at the same time with the same account. Add to this a sensible archiving software and you have a professional environment. Animated smilies are nice but perhaps not misson critical. Also I do not need a profile and stuff like this. Why bother?
For Donation and FAQ there can be a normal site. Keep it simple stupid. Just my two cents.