I don't think you can get vBulletin free but there are several others for free and which are pretty much the same.
Yabb SE is based on another BBS called Yabb (Yabb is written in Perl and YaBBse in PHP.
XMB is another free tool which is quite good.
I know of no ways of starting your own hosting company for free, I think the minimum cost wold be around 300-400 usd. All the companies I have seen that offer reseller plans require you to pay them in advance and you make your money (if at all) by selling sites to others.