I agree that you're allowed to combine such works. I was trying to point out that the project's top-level LICENSE file, which makes no mention of the GPL licen

I agree that you're allowed to combine such works. I was trying to point out that the project's top-level LICENSE file, which makes no mention of the GPL license that the combined work must be under: https://github.com/hal9000xp/euclid/blob/master/LICENSE https://github.com/hal9000xp/euclid/blob/master/LICENSE (From your link "[GPL licenses] also permit distribution of such combinations provided the combination is released under the same GNU GPL version")