Well no, you get 2 diff version of the SDK, and both of them you have to buy. One version is for C++, the other is .net
Its not exactly 2 different versions - the .Net part is a wrapper.
DGSDK is not a huge priority for TGC. You are gonna battle, and they arent gonna give you fixes or updates. And when/if they do, something else will be broken, and you will wait another year for an update
Whilst it did take ages to get the latest update, I suspect there will be another one before the end of the year. However, I do also suspect that the GSDK isn't a terrible high priority.