Re: buddypress on a certain blog
I have set up another blog only for buddypress due to create an online community.
You cannot set up BuddyPress on a single blog. BP is installed as a plugin suite for all of WPMU.
Each time I activate the plugin on the community’s backend page, it is also gets activated on every other blog I’ve created.
I’m not sure exactly what you are saying. BuddyPress will display (or list) all blogs, members can even access other members’ blogs, and there is a main sitewide blog. But, BP does not get activated on each blog.
You could write a custom function that will only display the main blog, filtering out all other members’ blogs, but I would imagine that your members will want to have their blogs accessible to everyone.