I encountered an obscure software license called the Maximum Use License for Everybody (MULE). (I have used text from version 4 below, but my concerns also apply to version 3.) The license first states:
- This software is "free" or "open source" software. It doesn't matter which of these names you call it. […]
but subsequent sections then state (emphasis added):
- You may use this software in any way you wish, subject to all applicable laws and to the provisions of this Maximum Use License for Everyone. You may copy and distribute all or part of this software, without cost, at will.
[…]
- You may give away, or sell at cost, an aggregate software distribution containing this software and software from other sources, without remunerating the copyright holder. If you give away, or sell at cost, a fully functional and readily available aggregate software distribution containing this software and software from other sources, then you may also include this software in an enhanced version of the same aggregate software distribution which may be sold for profit, without remunerating the copyright holder. However, if you sell copies of all or part of this software under any other circumstances, either alone or together with other works, you must reach an agreement with the copyright holder as to a reasonable rate of remuneration per copy (or a waiver of remuneration).
[…]
You may copy and distribute other software containing all or part of this software, in modified or unmodified form, without cost under this Maximum Use License for Everyone, or under any other "free" or "open source" software license consistent with the Open Source Definition promoted by the Open Source Initiative http://opensource.org/. However, if you sell any copies of such software (except as part of an aggregate software distribution under the circumstances specified in paragraph 4 of this license), you must reach an agreement with the copyright holder of this software as to a reasonable rate of remuneration per copy (or a waiver of remuneration).
You may also copy and distribute other software containing all or part of this software, in modified or unmodified form, under any software license that is not among the "free" or "open source" licenses to which paragraph 6 of this license refers, but only after reaching an agreement with the copyright holder as to a reasonable rate of remuneration per copy (or a waiver of remuneration).
I'm inclined to think this is not a legitimate FOSS (free or open source software) license due to contradictions with FOSS definitions, which prohibit licenses from restricting the sale of the software by any party. Overall, I think the author of this license is interpreting "free software" and "open source software" too broadly if not incorrectly throughout this license.
I also think that ability to relicense under a (recognized) FOSS license in paragraph 6 is impossible in practice, because recognized FOSS licenses will not allow the "without cost" provision to be enforced; the copyright holder of a MULE-licensed project would essentially have to allow sale by anybody without remuneration.