BuddyPress.org

Thesis is only a WordPress theme.

—

You don’t need to create a WordPress network if you don’t want users to create full-blown WordPress blogs.

If you want your users to post on a single WordPress install without creating a WP network, you might be interested in this thread:
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/user-blogs-without-multisite/