Well, this will be a guess on my part…
The program is available for sale on the homepage and so I imagine you buy it and download it.
The page states it is still in beta and I understand this to mean, that if you expect a fully-fledged program with no bugs, then you should wait until it leaves beta; otherwise, go ahead and buy it.
I have the program (through kickstarter) and it works well but there is still the odd bug. I have switched to using Worldographer instead of Hexographer and it works so much better.
There is – as with all programs – room for some improvements and new features, but I haven’t regretted getting the program.
Please notice, the above is me guessing – I am not in possession of the facts. 🙂