Best 2D Game engine

Looking to make a DM-esque platform game.  I was just wondering if there's a freeware indie game engine that you don't have to pay for.  I've already looked at spritecraft, and I tried to use it for a while until I realized it was bullshit in it's complexity; looked at PTK, and was amazed by it's simplicity in comparison.  However, you have to pay for it, like, 200 dollars.  This is a hobbyist game, I don't want to sell it or have to pay to make it. 

So, any response?

...um... is Abuse open-source yet?

Abuse was fucking awesome.

You probably need to wrap your mind around LISP, though, if you wish to script anything.  It's not as hard as you think.