If you want to transfer a license to a new domain, log in the download portal and load the license you want to transfer. The license details page will instruct you how to transfer the license to a new domain.
If you want transfer a license to a different installation of Recite CMS (but the same domain), simply load the license in the new installation. You can then optionally remove the license from the old installation.
The license is only accessible from a single domain, so it makes no difference either way if the old license is still loaded, since presumably the domain IP address will be updated to point the new server.