I don't know why you think you have to *buy* GSX Level 2 to continue to use GSX, since that's clearly not the case.
You must INSTALL the latest GSX (which contains GSX Level 2 files, which will installed in Trial version), if you want to continue to get *updates* to GSX and if you want to use the latest version of several FSDT sceneries that have been recently updated to feature SODE jetways, like JFK or KLAX but, nowhere we ever said you have to *buy* GSX Level 2, since all Level 2 features are always free to use at our airports.
If you just want to continue to use the basic GSX, go in the GSX Control Panel, and restore the Level 2 jetways, and you'll end up with the just basic GSX features.