Am I under obligation to develop this with openGl or DirectX? Also, would it be okay if the game was 2d?

I wouldn't think you'd be obligated to use either, but first I guess I'd have to ask what "this" is.

The 4 elements contest.

You can use either DirectX or OpenGL as long as it runs on the system specs stated in the main thread. And you can do either 2D or 3D. In fact, a lot of the entries are 2D, and I am looking forward to some of them the most :).

You don't have to use either (but may use either one if you wish), as long as it runs on the system specs listed on the contest page. 2d is fine, this is a game contest, not a graphics contest.

cool...I planned on having my entry fast enough to run on a 486..