The "user programs" you want to run are determined by the operating system. And the operating system is determined by blobs, controllers, BIOS and similar gunk

The "user programs" you want to run are determined by the operating system. And the operating system is determined by blobs, controllers, BIOS and similar gunk. If for example the Pi blob is such that Linux kernel 3.7 can't run then you are SOL. Or if on a device like this their blob only works with Android 2.3 then you can't run a different version. Or maybe you can't run one of the BSDs. The video/GPU is especially relevant in the Pi case because it controls what the CPU can do.