Daniel Bryan, real name Bryan Danielson, has let his contract expire after being with the WWE since 2009.

Before going to the WWE, Bryan Danielson would use “The Final Countdown” by Europe as his theme song.
While WWE has their theme music produced in their own studio, there are companies like All Elite Wrestling who will buy the rights to songs to use as themes.
For example, AEW’s owner Tony Khan, recently purchased the rights for one of the company’s most popular wrestlers, Orange Cassidy, to be able come out to “Where is my Mind?” by The Pixies.
So as long as Bryan Danielson stays a free agent, in theory, the rights to “The Final Countdown” is the most valuable it’s been in a decade.