I understood there was no pressure to release source code, I was just using source code overlap as a measure of similarity. An expiry time, like 10 years, soun

I understood there was no pressure to release source code, I was just using source code overlap as a measure of similarity. An expiry time, like 10 years, sounds a lot more reasonable. It's a bit like the expiry for copyright and pantents, at least in their original concepts. Come to think of it, maybe the solution is simply to dramatically reduce copyright expiry, maybe to a simple fixed 10 years for creation point. That would probably benefit everything, not just software.