BuddyBoss is the #1 open source platform focused on sell memberships, courses, and build online communities, giving you the flexibility, control and freedom you need, to create a successful online platform. The BuddyBoss team has created 2 fantastic solutions for online platforms:

1) A full featured plugin with tons of community-based features.
2) A beautiful theme to improve the design of its platform and with support with a great number of plugins.