Don't bother restricting people. There's so little traffic on this forum that you can't possibly be overwhelmed by a few spammers a week. On the other hand, restricting things might turn away new people. The forum is small enough as it is. Enlist some new admins or something if you need to.
I volunteer. I'm quite familiar with SMF, since I run it on
http://www.livebusinesschat.com/ and I'd really like to see this place grow.