Dual Licensing is based on the principle of Quid Pro Quo - something for something .

This is how it works: In return for the advantages you realize from using a Trolltech product to create your application, we require that you do one of the following:

• Either: Contribute to the continued development of the product by purchasing commercial licenses from Trolltech. This option secures you the right to distribute your application under the license terms of your choice.
• Or: Contribute to the Open Source community by placing your application under an Open Source license (e.g.  GPL version 2). This option secures all users the rights to obtain the application's full source code, modify it, and redistribute it.

By offering both open source and commercial licenses, Trolltech has been able to grow and thrive over the past ten years.

Trolltech Offers Both Commercial and Open Source Licenses

• Trolltech's Commercial licenses allow customers to develop, use and distribute their applications under standard commercial terms.
• Trolltech's Open Source versions are available under the terms of the GPL - General Public License (version 2). The main obligation for software development under the GPL is that anyone using your software must have access to complete source code, and must be able to modify and redistribute that software to anyone free of charge.
• Please note that it is necessary to choose either the Open Source or Commercial license at the outset of development. Trolltech's commercial license terms do not allow you to start developing proprietary software using the Open Source edition.

As a general rule:

• Based on the "Quid Pro Quo" principle, if you wish to derive a commercial advantage by not releasing your application under an open source license, you must purchase an appropriate number of commercial licenses from Trolltech. By purchasing commercial licenses, you are no longer obligated to publish your source code.
• If you wish to use an open source version of Trolltech's products, you must contribute all your source code to the open source community at large, according to the terms of the applicable open source license.

Why Does Trolltech Employ Dual Licensing?

Trolltech aims to make the best cross-platform development tools in the world. By selling commercial licenses, we are able to staff a full-time dedicated development team and are able to provide first class support.

By providing our products under open source licenses, we are also an active member of the open source community. This community has played an important role in ensuring the stability and quality of our products. Trolltech's products are thoroughly tested by thousands of open source developers around the world. Through active community participation in our development process, Trolltech products reach commercial stability far more quickly. We call this our Virtuous Cycle.

If you are unsure about Trolltech licensing, please contact us.