Hi Bastian, you are not paying anyone. If you decide to make a donation you are doing so to allow GPLDL to maintain a catalogue of unmodified premium WordPress items. They may or may not work as you attended and some may require serial numbers which cannot be provided here because we respect the developers’ TOS. Some people in the community may provide solutions of how to modify the code as you see above. If you do not like that or if it still does not work for you, we strongly recommend to buy a full license from the developers and support them.