I feel like I need to nitpick a little: Models don't need source code available to reproduce software. See all the "full decompilation" projects cropping up. There's no putting this genie back in the box, because LLMs can also "refurbish" a project enough that it ceases to look like the original. People don't bother now because they don't have to, but in a world where they'd get hit with copyright notices, they would.