A license defines the terms under which the copyright owner permits others to use their work.

On-topic

• programming licensing servers
• programming licensing clients
• implementing consumption of license keys

Off-topic

• Any licensing question where you did not write the licensing system. In other words, using licenses for other company's software (i.e. a Microsoft Windows license)

• Legal advice on usage of licenses. You may be able to get an answer to such questions at OpenSource.SE or Law.SE

Disclaimer

The answers are NO legal advice and there's NO warranty! For a legally valid advice consult a lawyer or another legal advice.