"Well, the people who wrote Wesnoth like to share the program with everyone. Not just what you see on the screen, but the code behind that that runs the game, and the artwork and everything. And Apple doesn't want to allow people to do that."
"Why do Apple not like people sharing stuff?"
"Because they think that people will pay them more money if they have to buy a separate one instead of sharing it."
"But it's free on the iTunes store?"
"Well, you still wouldn't get the code there, and you still couldn't modify it and put your version on your own iPhone."
"But I don't care about that, Daddy, I just want to run Wesnoth."
"Well, Apple really doesn't care about what you want, Rachel. They just want to make money. And they won't change their license rules even for Wesnoth."