How does migration Assistant handle licensing?

Migration Assistant does not handle licensing. The migrated and licensed application will determine if it is authorized on a new Mac with/out a license prompt, or new license purchase. It all depends on the per application licensing restrictions, and you should be aware of these before a migration occurs.

I doubt Migration Assistant "handles" licensing at all. It just copies files from one computer to another. If the license file gets transferred, it may or may to work.

If the apps have a licensing scheme that somehow knows what computer is using it, then it will fail and you'll have to take care of the licensing changes.

App Store apps are licensed to your AppleID, but they would not be tied to a particular computer, so I don't imagine that is what you are talking about.

I have used Migration Assistant many times. My experience is that some licensed software does work on the new computer after migration. I believe that is because that software stores the license key in a preferences file and as long as that preferences file is migrated over, it is recognized.

Other software uses more sophisticated licensing schemes. Some of them include a unique computer or hard drive identifier in their hash and hence the license key must be re-entered on the new computer. Sometimes that does not work because the software recognizes that it is still in use on the old computer and it must be removed or deactivated from the old computer first.

Older version of MS-Office used the less restrictive scheme, but newer versions check more carefully. Adobe software almost certainly needs to be reinstalled and license keys re-entered. Adobe has a way on its web site for you to deactivate all users of a license with one click, which makes this easier.