I must determine if you'll be able to add security to some WordPress theme offered online (something similar to an item license)?

I wish to make certain that when a style is offered, the customer are only able to apply it themself and never transfer or re-market it.

This does not always need to be a breach from the WordPress GPL license ...

Victor did not point out that he'd release it using blogging platforms.net - and there is commercial plug-inches and styles too.

The easy way make this happen is ionCube (or similar PHP encoders / code shields) + a vital-file certain to domain title.

But remember that this is not one hundredPercent secure solution, since it may be unwrapped / decoded very quickly.

Another method could be type of certification server - which triggers per domain-title - or transmits out 1 missing file upon effective activation.