We have sort of a Trial version but, the only way to activate it, is to have a license of at least one FSDT airport, in that case it will be possible to install GSX without a key, and it will work on any FSDT airport, plus 3 additional airports ( LIMC, EDDM and KSFO ).
We don't really advertise this feature, since more than a real Trial, it's a way for our users to use GSX for free at our airports, which has always been in previous versions. However, it is can in fact be used as a Trial.