The only game engine I'm actually familiar with is Game Maker Studio, is it ok to use it in this Jam? 

Already mentioned in another topic, you can use whatever engine you want, but open source are preferably seen.

I am in the same boat as you Pilocide. I will be using GM:Studio 2 (GML code) as well, its all I really know.

I personally use PhaserJS then the question is still asked in this thread

Hi there! Yes - you can use any game engine.

Yes you can use any game engine.