I've gotten several pull requests to my free hardware design that I sell as my primary source of income. Granted, a PCB change is difficult to test given the minimum order quantity, but other physical designs like cases are easy to do a one-off if you have access to a laser cutter or 3D printer.
As someone mentioned elsewhere in the comments, RMS thinks on a much longer time scale than you and I. Prototyping PCBs is already dramatically easier than it was ten years ago; I'm convinced the cost and MOQ will only continue to drop.
https://github.com/technomancy/atreus/pull/4
https://github.com/technomancy/atreus/pull/10
https://github.com/technomancy/atreus/pull/15
As someone mentioned elsewhere in the comments, RMS thinks on a much longer time scale than you and I. Prototyping PCBs is already dramatically easier than it was ten years ago; I'm convinced the cost and MOQ will only continue to drop.