Any combination of the following is available :
[1] GATE licensing : legally use
[2] Sample software : look at the source code and use that as a reference for GATE implementation
[3] Comprehensive training : learn how the GATE system works

For instance, if you think you can understand and implement GATE yourself, you can just license GATE and implement it without the sample software or comprehensive training.

Or if you don't want to license it but just want to buy the sample software, you can do just that and look at the sample source code [ in this case, without licensing, you cannot legally use GATE ]. Also, if someone just wants to learn the details of this innovation, they can do training without paying for licenses or buying software.

GATE can be licensed on a yearly basis. The longer, the better for you, since there is no guarantee that the price is fixed; it might go up as the system gets more popular. The longer the license, the more protection you have against price increases, at least for the amount of time it is licensed.