Are you saying that the executable you downloaded is only playable if using steam?
What happens if you try disconnecting the computer from the internet whilst running the executable or using another computer without steam installed?
I have attempted disconnecting from the Internet by unplugging my Ethernet cable. The game caused Steam to launch with my stored credentials but was unable to do anything that required Internet access. (Displaying the store page, showing the status of people on my friends list, etc.) The same error about not having a license popped up.
I do not have another computer at my disposal to attempt running the game there to see what happens.