swave is released under the MPL 2.0, which is a simple and modern weak copyleft license.

Here is the gist of the terms that are likely most important to you (disclaimer: the following points are not legally binding, only the license text itself is):

If you’d like to use swave as a library in your own applications
  • swave is safe for use in closed-source applications. The MPL share-alike terms do not apply to applications built on top of or with the help of swave.
  • You do not need a commercial license. The MPL applies to swave’s own source code, not your applications.
If you’d like to contribute to swave
  • You do not have to transfer any copyright.
  • You do not have to sign a CLA.
  • You can be sure that your contribution will always remain available in open-source form and will not become a closed-source commercial product (even though it might be used by such products!)

For more background info on the license please also see the official MPL 2.0 FAQ.