Common WordPress Question Answered: Do I Need to Enable Multisite to Run BuddyPress?
We get asked this question quite a bit, and it's a good question if you're new to WordPress and BuddyPress. The answer is no, you do not need to enable Multisite (formerly WordPress MU) in order to use BuddyPress. Only enable multisite if you want to provide a network wherein users each get their own blogs / sites.
In the early days of BuddyPress, the plugin required WPMU in order to run. However, since early 2010, BuddyPress is able to work with both single user WordPress and installations with Multisite enabled.
Simply put, you can run BuddyPress on any kind of WordPress site as long as you meet the minimum requirements.