Yes, you can use QuarkXPress on your primary computer and your laptop non-concurrently.It is called Dual Licensing which means end users who have purchased a single-user License may Install and Use the Software on two desktop computers for non-concurrent use only.
This is according to End User Licensing Agreement (EULA).For more information on EULA, go through the link - EULA.
It applies to QuarkXPress — all versions — Mac OS, Windows.