Posted by I’ve posted about the guys at www.multiwii.com in the past, these are the people that made affordable quadrocopter flight a reality for most people. The offer their code for free under GNU GPL (Open Source). You are free to use and modify and even make a profit with it as long as you keep it open and make your source code available. Very cool arrangement.
Unfortunately there is a controller called the Rabbit from China that has used the Multiwii source and is selling controllers for $100 and not releasing the source. A lot of people don’t care, they get a very well done flight controller for a good price and go on their way. Personally it pisses me off. It seems a LOT of people think it’s alright. I guess they wouldn’t mind driving a stolen car either, if they could get away with it. Here is the thread at RCGroups.