Vjylku

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:

1. 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):

2. 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.

[…]

4. 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).
   

[…]

6. 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).




7. 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.

Oh, good; yet another attempt by the crayon-wielding world to mesh free software ideology with the idea of non-commercial use. How well they all work.

IANAL/IANYL, but I agree with you that the licence is non-free, for the reasons you have stated.

However, I notice that s6, the section that allows re-distribution under any OSI-approved licence provided it is done at no cost, does not require a similar condition to be imposed on the recipient. So if you absolutely had to use some code licenced under MULE, my advice is to have a friend download it, and (per s6) convey it to you under GPLv3 (or, if (s)he must, some non-copyleft licence) without charge. At this point you have a properly-freely-licenced copy with no weird commercial restrictions, and life can proceed. However, it's probably best to avoid using this code if you can.

Forbidding sale of the software has precedent in OSI-approved licenses, for example SIL-OFL 1.1 says:

Neither the Font Software nor any of its individual components, in Original or Modified Versions, may be sold by itself.

But there is reason to believe the OFL is an outlier and wouldn't be OSI-approved if submitted today. Also, the OFL is only intended for fonts, not for software in general.

Back to the license at hand:

• MULE has never been put before the OSI for approval. Calling it an open source license is therefore a bit premature.


• MULE's author disagrees with the Debian Free Software Guidelines. However, the DFSG are the root of the Open Source Definition, and continue to be relevant in license evaluation. I would expect OSI to be hesitant to approve a license that would be shunned by Debian.


• MULE's royalty sharing provisions violate the DFSG's desert island test: How could a seller be able to reach a royalty agreement with the copyright holder unless they have communication channels and money transfer channels available? This is not necessarily a given, e.g. consider a potential seller in an isolated dictatorship.


• MULE's royalty sharing provision requires an agreement to be reached with the copyright holder. But there can be many copyright holders, because any contributor is a copyright holder as well. Reaching a royalty agreement with all of them would be unworkable.


• The author's references to the OSD try to lawyer around its particular phrasing (e.g. regarding “aggregate”), without taking into account the intention of this definition.


• MULE's relicensing provision is badly thought out. For example, MULE is clearly GPL-incompatible. Since the anti-monetization clause is supposed to stick around after relicensing, this relicensing mechanism is not sufficient to save the license from being non-open.

I therefore believe that it is incorrect to consider the MULE license to be open source, believe that it would never be approved as open source by the OSI, and believe no one should ever use this license.