I am interested to know if there are any laws or etiquette surrounding the use of people's third party plugins or QGIS itself. What I am especially interested in is when a user accesses your code and amends it for their own needs, or if someone could take the source code of QGIS and rename it for commercial use.

I am not planning to do any of these things and even if I did I don't have the skills - this question arised from a debate in the pub

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    Here is a quote from Boundless "if a user forks, the extra pain of upgrades will bring them back", in the very informative document Open Source Licenses Explained. While not about QGIS specifically, it describes several usage scenarios and the obligations under various Open Licenses. – JGH Jan 22 '19 at 12:28

There are many open source license type. Some allow to reuse in a commercial software, other don't. All will allow you to amend the code for your own need as long as you respect the other clauses of the licence.

Specifically for QGIS, the licence is the GNU General public Licence. It is a copyleft license, which means that derivative work can only be distributed under the same license terms. In other word, you cannot redistribute QGIS code under a proprietary licence, but you can make commercial use of the QGIS software. For sales or distribution, the entire source code need to be made available to end users, including any code changes and additions—in that case, copyleft is applied to ensure that end users retain the freedoms defined above

So, for example, you are allowed to sell a software based on QGIS with your own add on if it remains under the GPL licence. As it is under GPL, your software will be under GPL and your client can redistribute it under GPL if he wants. So if you want many clients you'd better offer some services around your distribution of the software.

EDIT: to give another example, GDAL is under the X11/MIT licence, which means that it is intended to give you permission to do whatever you want with the GDAL source code: download, modify, redistribute as you please, including building proprietary commercial software, no permission from anyone else is required. Most proprietary commercial GIS software use gdal.

  • you mean proprietary not commercial – Ian Turton Jan 22 '19 at 12:07
  • yes, I've corrected – radouxju Jan 22 '19 at 12:31

QGis is licenced using the GPL as are all plugins, so provided the end user abides by the terms of that license all is fine.

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