I've seen several threads about this here on the warrior forum, but never found a satisfying answer. I think the main problem will be that you can't 100% secure it, as it's all written in PHP and the license-check can be removed by anyone who knows their way around PHP.

But I would love to hear some good examples or services on wordpress plugin/theme license key implementation.

You have an answer - "don't bother".

Unless you use something like ioncube to encode the theme files, bypassing registration schemes in WP themes and plugins is child play and is pretty much a waste of time.

Even if you use ioncube or zend-encoding, it only elevates the difficulty to the teenage level.

I don't think he's looking to secure his code via encoder, he's looking for a good solution to implement a licensing module to create single and unlimited licenses for his wordpress plugin.
I wouldn't mind hearing some good suggestions too. It's a bit of a sandbox out there with the wordpress key/license function. It doesn't look like there is one big one out there that has established itself over everyone else. That's why he, and myself would love to hear from some others what they used.

That's why I said what I said - there is NOT a 'good solution'. PHP is not a compiled language, it's scripted, which means that some part however small, has to be in plain text. From there, it's just a matter of spending a little time decoding the obfuscated characters.

The only way to keep functionality from unlicensed users is to actually deliver a necessary part of the coding to the site from the authentication server. But that involves making an indefinite commitment to paying for and maintaining a dedicated server to deliver the code to make the theme or plugin function.

That is the basic functionality of the Akismet and VaultPress plugins from Automattic.

Good golly people....we just want to keep the honest people honest and a licensing system helps do just that. The Blackhatters will always crack it...that is not what I care about. Most "HONEST people will purchase and use a license.

Just need a simple solution. I understand this may work WP License, Wordpress Plugin and Theme Licensing Solution I haven't tried it yet, but may consider adding this functionality to my Software activation service | Software Defender since it seems to be such a huge problem.

Hope this helps
Rod