In reply to Gerd Neumann.

You should always purchase premium plugins from the developer who creates it and not 3rd party sites like gplclub.org, etc. The money you save could come back to bite you in the butt if the 3rd party that is reselling the plugin has manipulated the code in anyway, injected malware, or simply doesn't provide updates.

Because things like automatic updates for commercial plugins like Gravity Forms come from the developer itself, if you purchased it from a 3rd party... you wouldn't get automatic updates. Which means you wouldn't be receiving patches related to security, etc.

Definitely be hesitant of installing software from sites like that.

If you want to buy a plugin, buy it from the developer who created it.