Hello, devs and fellow CC fans;
I was wondering, what kind of graphical platform did the datarealms guys use, or did you make your own?
I've been looking closely into opengl and it seems very nice, but is it possible to do the kind of amazing stuff you guys did in the game with it?

Thanks for reading, please answer me if you can

I think he still uses the allegro library. Not sure though, this old post on allegro.cc from way back in 2006 seems to suggest it.

You should be able to find a list of all the technological platforms used in CC if you look toward the end of the Credits.txt within the main CC folder.

Also uh re: the question "is it possible to do all the awesome things you did in CC using openGL" - a resounding yes. Using raw openGL makes it possible to do a lot more than seen in cortex command, but will require a good knowledge of maths and progamming.
If you just want to get into programming and aren't looking to get very confused and overwhelmed, look into allegro (link above), SFML(sfml.org), or SDL(libsdl.org), which are all C libraries.
Perhaps more suitable for a new programmer, you could also look into the LOVE 2d game library which lets you write games in Lua (love2d.org).
A nice middle ground can be found in flash or java game development, though both have their headaches.

Basically - what has been done in cortex command would be easier to achieve with "lower level" programming for performance reasons, but requires knowledge of lower level programming languages like C, C++, or if you're really trying to squeeze performance, assembler. If you're just looking to get into game development, starting higher up (with a scripting language or something ECMAScript based) can help ease you into it, avoiding getting frustrated and quitting (which is the most common difficulty people seem to have).