Re: bbpress on flat-file
I think installing PHP and MySQL on localhost is beyond the scope of the bbPress support forums. Looks like you already found this:
It would be less stressful to just get a hosting account that already supports those PHP and MySQL, then install bbPress there. Then the site can be Internet accessible as well.
Regarding flat file forum software:
I don’t have experience with any of those, just found them at http://www.opensourcecms.com/
You could also use a hosted solution like Yahoo! Groups or something like that.