"The installer does have to obtain permission from the original STC holder."

Does anyone else see that as a possible problem? Obtaining the original STC costs money so I wouldn't be surprised if the holder might be reticent about letting people use it for free. As I understand it you need an STC for installing the unit in the aircraft and another STC to connect the ADS-B unit to the selected GPS source.

The ADS-B in function of the PowerFlarm has already paid for itself in my glider though and I fly in Canada where ADS-B isn't even on track to become mandatory.