License4J is a pure Java library for creating and validating licenses. The key concept is features of a license. You can easily add any feature to your license file, i.e. name of the product, version, expiry date, number of executable instances, customer's name, company, IP address, etc. The feature's value can be string or any serializable Java object. You can have unsigned features - features that are not used in the signature generation/verification and therefore can change their values leaving the license valid.

The new version has fixed MAC address retrieval on some unix-based platforms, serializable License class and is stronger obfuscated by Allatori Java Obfuscator v2.5

License4J home page and trial download.

Wouldn't be funny if this was released on GPLv3?

I was having a discussion about GPL on the Appcelerator community boards at http://community.appcelerator.org/message/8848;jsessionid=89C1945C82699A571C8321E88E583E05 about what the GPL really means for other open source projects. In particular Ext - an Ajax widgets project - switched to GPL v3 a few months back. It generated a fair amount of controversy. -Frank