Dual-license with GPL?

[sensorium]

Dual-license with GPL?

[sensorium]

My understanding is that if your application is non-commercial you can share Mozzi under CC-BY-NC-SA. What is the hurdle to combining with GPL code?

If you have a commercial application, we can negotiate a license.

[tfry-git]

I believe the problem is the following:

• If you create a work using ESP8266Audio, then you must license that under GPL.
• If you are create a work using Mozzi, then you must (in be absence of another agreement) license that under CC-BY-NC-SA.
• Although the two are similar in spirit, they are not compatible, thus you have no option to create a work using both ESP8266Audio and Mozzi.

One way out would be, if Mozzi would optionally allow you to distribute your derived work under GPL. I'd be sympathetic to that idea, but clearly it's your call, alone, to make.

[tfry-git]

I will add that the GPL does not preclude commercial use. All it says is that you must offer your source code under the GPL.

[DCooper-nz]

Would be great if this could be worked out as esp32 support would be fantastic.

[wyan]

What's the reason for the ESP8266 port not requiring ESP8266Audio but the ESP32 requiring it?

[tfry-git]

That comment was before support for the ESP32 was added to Mozzi (very recently). Neither port requires ESP8266Audio. Only the code the OP seemed to have in mind, did. The problem about a license clash if using both libs in the same project still stands.

[sensorium]

Hi, it's taking a while but I've been looking at licenses and I don't really understand how a dual license works, or how to present it with a project. Is there an example somewhere? Thanks...

[wyan]

The cases I know are products which are dual licenced GPL and a commercial licence. In those cases the customer can decide to use the GPL version for free, or, if they need to use the product in a commercial product that they don't want falling under the GPL, pay a licencing fee to obtain a non-GPL version. Some GPL products are kind of dual licenced as well, as they are licenced under "Version 2 of the GPL or any later version", at the choice of the user.

[tfry-git]

I believe the standard procedure is to provide separate license files (i.e. LICENSE.GPL and LICENSE.CC-BY-NC-SA) for the respective "standalone licenses". Then you'd create a third file LICENSE which contains something like

This work is dual-licensed under the terms of the CC-BY-NC-SA or alternatively under the terms of the GPL 2.0 (or any later version). Copies of these are distributed with the Mozzi sources as LICENSE.GPL and LICENSE.CC-BY-NC-SA, or can be found at upstream-license-url. You may use Mozzi according to either of these licenses as is most appropriatefor your project. (For - paid - commercial licensing options contact @sensorium.)

That short text (refined at bit) what also be included in the places where the license is stated right now, importantly file headers and README.

See also https://softwareengineering.stackexchange.com/questions/181040/how-to-document-a-dual-open-source-license , which has further variants and links to examples.