Official Gramps Project License
The Gramps project source files are released under the GNU General Public License, version 2 (GPLv2) or later license. The Gramps team wishes to promote reuse and openness of the Gramps codebase with other projects. The "GPLv2 or later" license was chosen because it is the most compatible with the other GNU licenses. The Gramps source code can be combined with code from other projects as long as the resulting code is used in a way that is compatible with both licenses. See the GNU license compatibility table for more information about license compatibility.
3rd Party Addon License
Gramps makes no requirement that 3rd party addons use the same license as the code in the official Gramps repository. However, addon authors should be aware of how their selection of license may empower or limit the use of their code in the future.
Project License Implications
This section provides some examples of how the Gramps source code can be used. These use cases demonstrate implications that result from the Gramps Project License.
3rd Party Addon Promotions
If a 3rd party addon becomes popular, it may be advantageous to add it to the official source repository for distribution with the core code. However, in order for the addon to be distributed with the core source code, the addon must already be released under the "GPLv2 or later" license.
It seems likely that in the near future it will be possible to use Gramps over the Internet as a web application. When this functionality is available, it would be possible for a person or organization to host the source code on their own server, make changes to the source code, and never contribute those changes back to the project. This type of use is allowed by GPLv2, and as long as that person is using Gramps in a way that is compatible with GPLv2, they are allowed to keep their source code changes.
Some people may see this possibility as a disadvantage because there is a risk that someone will use the code to their advantage and never contribute back. The Gramps project contributors are aware of the risk and if it were ever to become a problem, the project could choose to exercise the "or later" part of the license and release Gramps under the Affero GPL or some other more restrictive license.
Will Gramps Ever Change to GPLv3?
Because the Gramps Project License is "GPLv2 or later", the project has the option at any time to start releasing code under "GPLv3" or "GPLv3 or later". The topic comes up from time to time, but there are no plans at this time to change the license.