I'm thinking of buying a Raspberry Pi and putting some open source OS/kernel on it so I can modify it into my own OS with my own apps. The device would be a simple PC that I can pull out of my pocket and use for music composing, programming and pixel art drawing.
I've been programming for 5 years, learned C and C++ from ground up with malloc, structs and classes and worked on a software based debugger for AVR microcontrollers that have no MMU or enough space for malloc.
Therefore, the software challenges don't matter if I can quickly learn about the OS to modify it into my own work in a deadline of 3 months.
What matters most is that I must be able to sell parts of the software, the device and license them in such a license that doesn't forbid other people from using their own licenses which aren't viral for their own projects. GPL is a very big forbidder in this case. The two OS's I know for ARM are Linux and Android. Linux is GPL so I don't like it. I'd like to tweak around the kernel, but that means my stuff must be GPL-ized. I don't like Android either because it shuts down apps by its own decision (sidejoke: maybe it's a robot(android) thinking for itself and going against humanity). I've had Android phones and they're a pain to use. More faulty in multitasking than a regular feature phone with lots of features and J2ME functions like Sony Ericsson C510 which I'm trying to make an alternative for.
Which OS should I use?