I disagree. I consider practical limitations and legal limitations to be not be a subset of the other. They are separate, and the respective freedoms are both important.

And I dispute your claim that in the rom hacking community something "awfully close" to source code was often available. Plenty of times, mods are done using disassembly from the binaries. Disassembly is nothing like source code. Yet software patches based only on disassembly are possible, maybe even common. Source availability of course makes things easier. Documentation makes things easier still. Public version control of source code makes things eaven easier.