This isn't just a free software problem. Assigning credit is hard. Mathematics arguably has this problem, too. Important problems take decades or centuries,

This isn't just a free software problem. Assigning credit is hard. Mathematics arguably has this problem, too. Important problems take decades or centuries, and a long series of discoveries are necessary to put us in a place where the final step is in reach for a single person or team. Perelman rejected the Clay math prize for exactly this reason. And this is in a field where citation and attribution are carefully recorded in the literature.