Have any of you guys gone though the process of getting source code for a device in order to make custom roms?

Isn't it typically just kernel sources that would need to be released under GPL? A custom kernel is typically a few steps later in bringing up a custom rom for a device. The existing build is probably enough to try and get twrp running if you can get the bootloader unlocked.

Edit: All the same, very noble. Best of luck getting the sources, and making something useful of them.