What are the requirements to unlock "License Game Engines" research?

I've seem to have researched, done and released everything there is in the game except the licensing out engine. I've never got the research for it. Everything else is pretty much maxed out, all the research, most of the employee training and such. So I'm a bit lost...

The only thing that I might be missing is the perfect game achievement, there's always someone who will give it a 9 >_<

I believe you unlock that research when you create 10-12 custom game engines. Here is a similar question with more information about them.

You need a Research Lab and to create 10 Custom Engines.

Here is more information: Research Unlocks