I can confirm that you must have a separate license for UE and for UE Mobile. The licenses are exclusive for those 2 products. I had to get separate licenses for each when purchasing.
Although now that I have a new laptop, I never seem to need UE Mobile any longer, unless someone asks me to help them with something on their computer. Then I bring my own set of portable tools, which is why I still keep UE Mobile around.
I prefer the full version on my machine when I'm not using someone else's computer, because it gives me the added benefit of having it integrated into the explorer context menu, etc.
Also, with the mobile versions of UE Mobile and UC Mobile, they don't interact as well as the installed versions. This is not IDM's fault, but due to the way PortableApps are required to be set up. It's just the nature of the beast.
“Don’t document the problem, fix it.” – Atli Björgvin Oddsson