@Wong - Err, I don't recall Duke Nukem being grid based, it used the commander keen engine as far as I can remember, and that was "free" movement so to speak.
As far as what products you can use, it has to be click products. (This INCLUDES Jamagic).
I'll get to the rest as soon as work calms down a bit.
Not all of it was on a grid, but I'm fairly sure that Duke could only be on a 16x16 block (or thereabouts) or half-off it.
Similarly, Prince of Persia wasn't based on a grid for the PC/Amiga version, but the Gameboy one might have been (the character could only be in the middle or edge of platforms).
Ok, for submitting your entries; not until after the contest deadline (So you can post them starting on Xmas Eve).
Just so you guys know, this weekend there will be an actual Compo Page that will have ALL the updated info on it; so keep these questions coming so I can make sure that the page will cover most of my bases.
IIRC Duke was meant to use the Keen engine like Bio Hazard did but the dude ended up writing a similar one from scratch for some reason. But no, not grid-based.