John Tiller's website and store.
All other John Tiller titles are available from HPS Simulations at this time. It will be interesting to see where this goes. Has John Tiller parted from HPS?
Kharkov 43 has some minor differences from the other Panzer Campaigns titles but it is still Panzer Campaigns.
The new game has a moderate DRM device on it: you are given a serial number and with it you can activate it via the internet. Apparently you can only have one copy of the game installed at a time.
Some screenshots follow. Another fine study of the Eastern Front.