Havok is best known for its physics middleware, but in 2013 it made an entrance into the competitive game engine market with Project Anarchy. Three years later Havok has made the decision to "conclude" Project Anarchy, shutting down the engine and site.
If you hit up the official site, you'll hit a redirect page with the following message:
PROJECT ANARCHY™ HAS CONCLUDED Download access, forum access and the Project Anarchy™ website are no longer available, however, if you are currently developing using Project Anarchy™ you may continue to do so under the terms of the Project Anarchy End User License Agreement. We want to take this opportunity to thank all Anarchists for your participation and contributions to the Project. If you have any queries or questions please contact us at firstname.lastname@example.org
Project Anarchy was much like other "all-in-one" game engines and featured an integrated editor with tools for animation, particles, debugging and of course, physics. It differentiated itself by being not only free, but having no revenue cap.
From what I can tell, not many Project Anarchy-powered games were publicly released — which likely had an impact on its demise. The most recent appears to be a PC title called Cosmonautica, released in July 2015.
Project Anarchy [Official site]