My 2 cents. Something to think about.
if I just unregister the keylab from my arturia account/email, and give my friend the keyboard registration number to put it into his account? (that way he gets my extra bundled software copy of analog lab).
Doing so by own choice, then you in legal rights give away your controller. You will no longer have any rights in term of support or warranty either.
The owner of the controller have the right to the bundled software and other benefits - that might also include better product offers.
Also if you do like you suggest, then it would be cheating - not legal, as it's only to seperate the bundle. Also your friend can claim you have stolen the controller given as a gift by you. Your license transfer is will be the proof.
I would not transfer any license or registration.
You (the owner) have the right to the availble product activations on the owners units.
I suggest you keep your registrations and licenses for your self on your (the owners) account. Have safety in mind.