building a large system around vb

[tefnut]

This should probably go into the hacking/heavy modding forums, but I'm not allowed to post there , so here it goes. I plan to build a very large community-centered system with a database of information, and greatly expand on the profiles. The main reason for using a bulletin board backend is for the handy user/login that's already built in, and the commenting can be extended to, say, news articles postings or photos. Think of it as my own PostNuke, starting with vB barebones.

Some questions

- How receptive is vB to changes and how friendly is it to the average programmer? There is no developer documentation for what I've seen, but there does seem to be a healthy community and effort here.
- Is the copyright concern especially stringent, as in, will I have trouble actually using a lot of separate databases with vB's code and login system, or will it allow for a lot of extra coding on it?
- Has anyone built or know of sites that have greatly expanded on vB's structure? I've seen a journal/blog type thing implemented, and that's part of what I want to do, only to a lot further extent.
- What's the best forum software suited for this? Off the top of my head, I can think of vB, Invision Power Board and phpBB. Anyone have experience between these (or others) and recommend the most well documented, well coded and receptive system? From what I see it seems to be vB.

I guess my only worry is that I'll never understand the details of the vB code without the proper documentation