License4J is a pure Java library for creating and validating licenses.
BSEditor: 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, customers name, Company, IP address, etc. The features 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.

Also the library provides methods for signing arbitrary content that should not be changed by the user.

For the maximum Protection of your application it is highly recommended to use Allatori Java Obfuscator together with the License4J library.

Advantages
Ease of use
Straightforward API
Use of public key standard methods
Complete documentation
Compatible with JDK 1.3, JDK 1.4, JDK 1.5 and JDK 1.6
Backward compatibility
Free email support for 12 months
Free updates and upgrades for 12 months
No royalty or runtime fees you can free download License4J 1.5 now.