Comment by ekidd

It has been decades since I've seen an FSF CLA packet, but if I recall correctly, the FSF also made legally-binding promises back to the original copyright holder, promising to distribute the code under some kind of "free" (libre, not gratuit) license in the future. This would have allowed them to switch from GPL 2 to GPL 3, or even to an MIT license. But it wouldn't have allowed them to make the software proprietary.

But like I said, it has been decades since I've seen any of their paperwork, and memory is fallible.