Good question Rich,
DB pro is a good programming language to start out with for making games. It can make any game that you can imagine, anyway you want it to be. Weather it is a 3D or 2D game it can be done with DB pro, The sky's the limit.
If you purchase DB pro and register it, any software or game YOU make with it is royalty free. By YOU i mean the code and any 2D or 3D graphics that you make or get for free.
As for selling games made with DB-pro that's something you'll have to figure out, since its the program code is BASIC the only thing the games can be run on are computers. So selling for mobile devices and etc, is out of the question.
The only way i figured out to sell a DB pro game would be if a you personally distributed it via a web site.
If you have you're heart set out on getting DB pro i would recommend the Dark game studio, i got it when i was 15 and it was great to learn with and had a bunch of game making goodies that came along with it.
BTW: If you don't already know how to code in BASIC i recommend buying a book on it, something like this:
http://www.amazon.com/DarkBASIC-Programming-Absolute-Experience-Technology/dp/1598633856/ref=pd_sim_b_1/177-6415702-5486368
Its a great book that makes learning programming fun and easy!
If you want something that will be more easy to sell your games, i recommend App Game Kit .
http://www.appgamekit.com/
Its a great app making IDE that can make you some money, from any mobile device market like the android market, Intel app up, or Samsung. from what ive read its a little easier to use with more commands. Although at the moment App game kit only supports 2D commands (you can only make 2D games), but im sure that 3D commands will be out some time soon in the future.
Well that's all the info i have give, the choice is up to you my friend!
Programming and video games, what else could you need?