Generally, the “Remove” button on the InterMapper RemoteAcess Registration dialog should work, but we had a customer report this wasn't working. I thought it would be beneficial to add this to our forums in the chance someone else may run into this. 

For Macs, the license should be located at ~/Library/Preferences/

A discussion forum said also to look in /Library/Preferences/ as well (probably that same file name.)
Note: The plist files are no longer text XML files, unlike older Mac versions, so you cannot edit them with a text editor. It sounds like you can edit them with Xcode.

If you don’t see it there, then we need to check and see if the license was installed by an admin. If it was, you will need to change the permissions.

cd /Library/Preferences
ls -l // see if the file exists and what the permissions are on it.
sudo chmod +rw

Then try the “Remove” button in the InterMapper RemoteAccess Registration dialog and see what happens.