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I'm about to release a GPL licensed application framework and am planning on dual-licensing with a proprietary license. I'm wondering if the GPL classpath exception could be used as a basis for a simple license.

I would like the ability to separate support contracts and other typical proprietary software license clauses, indemnities and such, from the simple permission to write proprietary software using the framework.

The following example text is based on the GPL linking exception.

The copyright holders of this library give COMPANY permission to link VERSION of this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of their choice, provided that COMPANY also meets, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. COMPANY may not extend this permission to its version of the library, whether the library has been modified or not.

Is this viable? Any pros or cons?

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    The GPL already is a non-exclusive license, and the copyright holders can issue alternative licenses directly. However, things do get more complicated if there are multiple copyright holders, for example if the library includes third-party GPL material or if people contribute to the library. Then, the typical approach would be to have all other copyright holders sign a CLA that licenses the necessary rights. But that would probably have to involve lawyers. Writing your own licenses (or as in your question, GPL exceptions) is dangerous, in the sense that they might not have the desired effect.
    – amon
    Sep 18, 2023 at 20:42
  • Leaving the dual-licensing for contributors issue aside (about which amon writes very sensibly above), is there any reason why LGPL wouldn't work for your copyleft licensing option? It's essentially identical to GPL + linking exception, and it's better-understood than GPL + any custom exception, which makes adoption more likely.
    – MadHatter
    Sep 19, 2023 at 8:14
  • I am the sole copyright holder of the library and will not be accepting code contributions without a CLA to be able to dual-license. Conerning the LGPL, I want to SELL the permission to use my framework in proprietary software not give it to everyone, which is what the LGPL would do, right? My thinking is that the classpath exception being very well established (e.g. Java) that basing a minimalistic license on it should be safe.
    – darri
    Sep 19, 2023 at 8:45

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No. I would strongly recommend against tacking such a non transferable exception clause to the GPL. I don't see any pro and only a lot of cons.

The general expectation of GPL+exception is that you can re-distribute the work under the same license, but that is not the case for your exception. That alone will likely cause confusion and probably unintended license violations.

The way you have written your exception, with an explicit mention of the recipient and version, means that you will have a lot of administrative work to do, especially if you adhere to the common practice of mentioning the exception in every single source file.

I would recommend that you do a proper dual licensing, with the plain GPL for the free version and a properly written proprietary license for the paid version. And as a license is a legal document, you should ask a lawyer to write your proprietary license.

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  • Or, to my mind, straight LGPL for the free version. +1 from me.
    – MadHatter
    Sep 19, 2023 at 10:51
  • I assumed it would be enough for the recipient to include the exception file they acquired from me, in their application, which could then be linked with the GPL version of my framework and distributed with a license of their choosing. And yes, I will definitely be talking to a lawyer before committing to anything like this, right now I'm just looking at the options available. I'm also under the impression that by using the LGPL as suggested by @MadHatter, then anyone could use my framework in proprietary software, thereby eliminating the possibility of monetization.
    – darri
    Sep 19, 2023 at 11:46
  • They could do that using the licence exception you provide above, as well ("copy and distribute the resulting executable under terms of their choice"). I thought that's what you intended.
    – MadHatter
    Sep 19, 2023 at 11:52
  • I'd want to sell this license exception on a per company basis, the company being specified in the license text, meaning that specific company can "copy and distribute the resulting executable under terms of their choice", but anyone else using my framework without such an exception license, would still have to distribute their software under the GPL. My intention is not having pages and pages of legalese in a license, when all I'm trying to offer is this specific exception, allowing proprietary usage for a fee.
    – darri
    Sep 19, 2023 at 12:29
  • @darri, if a company makes use of that exception, others would not be able to redistribute the executable at all, because they would need to do so under the GPL but the executable will most likely contain GPL-incompatible parts. Sep 19, 2023 at 13:20

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