Thanks for writing in!
Transferring license from one website to another is same ass validating a website.
Just go to Apex Dashboard -> License and assign the new website to the license you want to transfer.
Then go to the new website dashboard and validate the site.
Check out the product validation guide.
After you validate the new website the old website the old website won't be validated any more.
The license I'm transferring FROM will no longer be in existence.
I am really confused about this questions. Are you trying to transfer the license from one account to another?
If so you just need to unlock your license from your license page.
Then login to your another account and register the license over there.
In this case, the license will be completely removed from your old account.