Folks, just to clear up a few things, virtually everything application-wise that is written for phpNuke is GPL and may be freely distributed and modified as long as you keep the original credits. People can charge a nominal amount for the d/l of it but then the next guy can give it away. Applications like NukeSentinel™, AutoTheme, phpNuke (Club), E-Solutions, Emporium, etc., - these are all GPL regardless of what they may say. If you pay to have a theme/application built, the developer can sell it to someone else if they want, all but the images (or so it appears). Like it or not, that's the reality. And if a phpNuke script is encoded, the author must, by the rules of the GPL, provide an unencoded version at your request.

For more discussion on this, see
Can developers legally sell addons created for use with Nuke?
Can you legally request money for 3rd party Nuke software (synopsis)?Note:
Please note that while there are professional, ethical, and even moral implications and issues, imo, the legality is that it is and remains GPL as long as it requires a GPL application to function.