Xara have added the ability to manage your own product activations on their support website, but looks like everyone is limited to a maximum of 2 activations. The EULA now says:

"You will be issued with a unique serial number. An internet connection is required to activate the serial number and to complete the necessary one-time registration. The Software can only be activated on two computers concurrently, but activations that are no longer required can be cancelled so that you can install and activate the software on a new computer."