Multisite and Buddypress- can you offer BP to just a few on your network?

If I set up a network site, and choose to NOT use BP for my main site, and some other site I might set up, can I still make BP available to others that might sign up and want BP?

Will they get along is this way?

Also, I noticed some business themes that I installed. Then when I was in the admin/Themes I noticed that they now had Buddypress in the names of the themes. Does this mean that they can ONLY work with BP?

Thanks,
Tom