Yes, you will need to purchase Axon. It used to be free, however there is now a license cost, although I should probably double check to see if a free version is still available.
As for Express Talk, same thing. There used to be a free version, but I'm not sure if there still is. In any case, I doubt if the free version allows/ed the use of the intercom function.
Remember that you can always test out NCH software before buying (no limitations) to make sure it works exactly as expected. Also note that bulk license discounts are available.
-Sent from my iPhone