I like how they never even gave money to the guy that built the physics engine powering their whole schtick. He only asked for a shirt--when they finally sent him one, it wasn't the one he'd asked for. Stay classy Rovio!
I didn't know you were supposed to pay for using free software. Regarding the color he didn't ask for anything, they just sent him a red one after which he said that he didn't like the color.
When you've made as much money as they did off of something that is largely a tech demo for somebody's free software project, I think it's only right to show your appreciation for that person--at least offering a well-paying job or fellowship or something. Otherwise, you're just being mooches.
Definitely but I'm pretty sure the maker of Box2D has no problem finding jobs. Would you really give money if you were Rovio? How much? Genuine question. Would you do the same for every author of free software you were using? I'm guessing that would be thousands of people.