BuddyPress.org

Once again, GPL does not mean that something is for free. Programmers can charge for their work. Once the end-consumer has the code he or she can do whatever they want with the plugin, because the code is GPL. I would argue that you will get a an even better and healthier plugin environment with paid for add-ons in the mix. These programmers try to live from their work and it will be in their best interest to provide first-class support, whereas authors of free plugins might only fix bugs if they have the time to do it. One of the best examples for this is Gravity Forms. Excellent plugin, great support, fair price.

Just some food for thought…