Steps:

  1. Activate your new LS in the new domain
  2. Move your licenses to the new LS from old LS
  3. Deactivate old LS in the other domain
  4. Adjust LS discovery process in the old and new domains to use new LS

Resources:

How to move Terminal Services CALs from one license server to another in Windows Server 2003 or in Windows 2000 Server

http://support.microsoft.com/kb/953918

814593 - HOW TO: Deactivate or Reactivate a License Server Using Terminal Services Licensing

http://support.microsoft.com/?kbid=814593

279561 - How to Override the License Server Discovery Process in Windows Server 2003 Terminal Services

http://support.microsoft.com/?kbid=279561