At the moment we are writing modules for an open source cms. We would like to sell these with a license.
But which are the best options? Any suggestions and experiences.
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First off, you'll need to look at the licence for the CMS and whether it allows you to do this.
Unlike the various open-source licences (creative commons, GPL, BSD, Apache, Mozilla Public Licence, Perl...) there is no standard licencing terms avaialble off-the-shelf. Indeed, most commercial licences have explicit terms convering the licence itself - and even where that is not the case, they will be covered by copyright.
Open source licences do not prevent you from charging for the software. Some affect the users rights for redistribution / modification. Microsoft admit that piracy of their software has probably been a net benefit to them via acquiring market share. Have a google for the discussions on GPLv3.
If possible, GPLv3 will allow your software to be redistributed, but not allow other people to charge a premium for redistributing it or providing a service based on it. This of course does not preclude you from offering the product under a different licence (which you can explicitly promote via the GPV3 version).
And under most of the open-source licences you can still charge for support.
Check if you can sell them with the license of the CMS. If it's possible, you can sell them with that license.
Options depend on what you can do and what you want to achieve. You have not told with your question, so that part can not be specifically answered.
Normally all licenses that allow commercial re-distribution of modified works should be suitable.