WeSIP

From Wesip

WeSIP is FREE for non-commercial use. That means that you can use it for any kind project you can think of as long as you don't make money out of it. Developers of commercial projects can use it as well to develop their commercial applications but not to deploy them.

Commercial licenses will be available soon including additional features and of course commited support. Anyway, if you can't wait for longer please fell free to contact us.

The text of the license is here