IntenseLogic ArchiveLast Updated: September 10, 2020
IntenseLogic is a game engine that I worked on several years ago. Development started on May 23, 2012 and continued up until the last functional change on December 24, 2015.
It's written in C, and originally had a Lua scripting API, although this was eventually abandoned.
The original goal was to be a competitor to Roblox with more powerful Lua scripting. This was in 2012, when Roblox was more of a Lego building game with user-made levels, than the game platform that it is today.