##License Plugins under a GPL Compatible License
Add-Ons *should* be licensed under a WordPress-compatible license. This enabled them being able to be re-distributed with WordPress as one software program. A fitting one is the GPL itself. Take care that all code libraries included with the plugin are compatible with that license too.

(This has [been a problem][1] and serious [point of debate][2] in the past and even [very currently][3].) 


  [1]: http://wordpress.stackexchange.com/questions/377/gpl-and-plugins
  [2]: http://wordpress.stackexchange.com/questions/5/am-i-allowed-to-license-my-wordpress-theme-under-the-agpl
  [3]: http://core.trac.wordpress.org/ticket/14685