If my main site is NOT buddyPress?

Can people install buddypress plugin in my Multisite Network

environment? or does it need to be a seperate system altogether or do i need to START with BuddyPress as my main site network?

When i use the wpmudev dashboard it will not let me install as a plugin on the fly just lets me download or gives me a two step process to install? the plugin has an x by it and says for BuddyPress only.?