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Your question is based on a common assumption, that you asked about a couple of days ago. In the US, at least, there are two ways multiple people can hold copyright on something: (1) if each contribution is independent, like a magazine or encyclopedia article, you have a collective copyright; (2) if each contribution is meant to merge with the others, you have a joint copyright. The rules for collective copyrights are basically what programmers seem to expect for collaborative works: each contributor owns copyright on their particular contribution. However, I believe most open source projects are actually joint works, and the rules for joint copyrights are wildly different from what programmers seem to expect (e.g., http://copyright.universityofcalifornia.edu/ownership/joint-... , but you can find other explanations online, including at http://copyright.gov ). It's clear to me that the law assumes people who collaborate on a joint work will have some kind of agreement between them, like a CLA. I'm not able to find it right now, but I'm aware of one case where somebody contributed to a proprietary program, declared that made him a joint copyright holder, and started selling copies of the software without permission. The court agreed that if he had been a joint owner he would have had authority to sell copies without coordinating with the other owners, but the court decided he only had copyright in his contribution, like a collective work, not because the contribution could stand alone, but because it was relatively small and easily identified. Based on that ruling, if I maintained an open source project under some kind of restrictive license that I intended to enforce, I wouldn't worry about getting a CLA for small patches (aside from getting some statement that they had authority to offer the contribution), but I would worry about getting one from regular contributors. There is some point when a contributor crosses a threshold and becomes a joint owner. You want a clear agreement between the joint owners, but I don't believe the license is the right place for that agreement. |