Axon Framework is licensed under the Apache 2 license. The full terms of that license can be downloaded here.
These terms basically allow you to use the framework in any application, for free. You may also make changes to the source code, as long as the license notifications in each file are kept intact. Of course, we’d like to receive feedback on the files you’ve changed, so that the community can benefit from the work you’ve done (just like you benefit from the work we’ve done), but you’re not obliged to.
On the other side, this license also means that the software is as-is and no guarantees are provided about the quality of the product. Of course, we will try our best to prevent bugs and to fix them as soon as possible when they are detected. But we’re not liable for any damage cause by the use of Axon.
It is not unimaginable that you’re using Axon in -let’s say- critical, high performance and scalable applications. In such circumstances, it may be useful to opt for better guarantees. Trifork supports Axon Framework and provides commercial services, such as support contracts, training and consultancy. If you’re interested in these services, visit the Trifork website.