Difficult. you need to activate over the internet. Licences are per 'locale'. if you move a licence from let's say USA to Australia they will detect it.
it's not easy to transfer licences.
Other problem is that most people run upgrades so the base key is still linked to their account.
for example let's say bought protel 99se and then upgraded to dxp , dxp2004 all the way through Altium 15 now. The base key for protel 99se is still the same base key for my altium 15 ...
Altium uses two keys for licencing. One is the install key , the other is the user key. So they can trace my user key down to protel 99 ...
The moment you register Protel99 they will detect the base key and pin you on locale. There is a transfer fee. And then the user key will get you in trouble as that is assigned to the company that originally bought it. It is a mess.
So you will have to find someone who doesn't use it anymore.... get a letter that they sold the licence to you and then go with that to altium to release the lock and assign it to you.