Dual Licensing is based on the principle of Give-and-take: in return for the advantages you realize from using VMime to create your application, we require that you do one of the following:
- Contribute to the continued development of the product by purchasing commercial licenses from VMime. This option secures you the right to distribute your application under the license terms of your choice.
- Contribute to the Open Source community by releasing your application under the GNU GPL license. This option secures all users the rights to obtain the application’s full source code, modify it, and redistribute it.
What license is right for me?
If you derive a commercial advantage by having a closed source solution, you must purchase an appropriate number of commercial licenses for VMime. By purchasing commercial licenses, you are no longer obligated to publish your source code. However, you are required to publish any change made to the VMime codebase (ie. files included in the VMime distribution package) and give everyone the right to use and share it.
If you wish to use the Open Source license of VMime, you must contribute all your source code to the Open Source community (ie. release your code under the GNU GPL license) and you must give them the right to share it with everyone too. To know more about GPL compliance, please read the Practical Guide to GPL Compliance.