Can I make a commercial game with Blitz and are there any royalties to pay?Yes you most certainly can. There are many commercial Blitz titles on the market currently both in shops and online (3d and 2d games).
You are free to sell your games in any way you see fit without any royalty payments to anyone (assuming the graphics and sound you use are yours!).
Addition: Please note that you may have to pay license fees to other companies if you include:
· BSP maps compiled with Id Software tools
· MP3 files