I purchased the Honolulu airport in Jan. 2013 and was told that GSX was FREE since parkme was discontinued. I not sure that's correct.
GSX IS FREE, at Honolulu, and on any other FSDT airport, plus all Flightbeam airports, and two Trial airports too (LIML and EDDM).
You got that message when you were parked at Honolulu, because you pressed the ParkMe key. That message said that, since you were trying to use a function of the scenery (ParkMe) which has been replaced by GSX, and GSX is free to use THERE (and at all FSDT airports), you were suggested to download GSX.
Since GSX is free to use at all FSDT airports, there's no reason not to download it, if you own any of them.
It does not work on non fsdt airports within FSX. Do I have to pay for GSX to get it to work on the other FSX airports? If so, is there a discount on the cost of 29.90 Euro?
I believe it's not possible to be mistaken by what is indicated on the GSX page:
http://www.fsdreamteam.com/products_gsx.htmlGSX works FOR FREE AT ALL FSDT AIRPORTS, because it greatly enhances the previous ParkMe™ feature, and it integrates perfectly with our airports.
Purchasing GSX, will enable to use it at ALL FSX Airports, both default and 3rd party, even those not released yet
We clearly indicate that GSX is free to use at FSDT airports, nowhere we say that, by purchasing an FSDT airport, you get GSX for free, they are two very different things.
If so, is there a discount on the cost of 29.90 Euro?
Yes, there's a discount applied automatically, but only if you purchase it TOGETHER with another product, in the same order, as explained here:
http://www.fsdreamteam.com/forum/index.php?board=12.0