Licensing

[tiagovignatti]

Any chance to change the license to something more permissive, say MIT? I'm considering using OpenPLC as a plugin for a commercial usage sw but I'm pondering whether it's possible due its licensing requirements. Thanks anyway, it's a great piece of sw!

[thiagoralves]

As far as I know the biggest difference with GPL and MIT is that if you make modifications to the code, the GPL license requires you to distribute your modifications as open source. If you are just using OpenPLC as a plugin, without any modification, I don't think it would be a problem, even with the GPL license. You don't have to open source your entire platform just because you are loading an open source GPL plugin. However, if you need to modify OpenPLC in some form to be "loadable" by your platform as a plugin, then these modifications need to be open sourced as the original project. I like the GPL license because whoever use OpenPLC and modify it, will have to give the modified code back to the community.

[tiagovignatti]

I see. So if I build a hypothetical software (or SaaS) containing an unmodified version of OpenPLC, is it okay to sell while keeping it as closed source? Thanks again and sorry to disturb you with that but I need to double-check this before anything :)

[blm768]

Based on my own knowledge of the GPL, the only issue I can see is if you were to either modify the OpenPLC code or have your own code link to part of OpenPLC. If you use OpenPLC unmodified as an "external" binary, it's very similar to embedding a GNU/Linux system in a closed device, which is a common practice.

As a side note, the LGPL and Apache license are good "middle ground" options that would permit linking with closed-source code (but still require you to share changes to the OpenPLC code itself). But technically, changing the project's license would require the agreement of all contributors if they haven't officially transferred their copyrights to @thiagoralves.

[GhostofGoes]

If you directly integrate proprietary external code as a hardware device, then the entire code, including the proprietary module, must be "open-sourced" under GPL. This makes it problematic for a company to use this in an effective manner with their products.

History has shown that companies will often still contribute to open-source portions of their applications. If you want companies to start using this (and thus contributing code to it), I think @blm768 has the right idea.