Max 1 user and activated in 2 computers. To activate on the 3rd system, you need to go to your Magix.com account, and then deactivate one of two previous activations.
According to this, MAGIX allows for 2 installs on 2 systems. And according to Nick's FAQ (point 9.), "You can use MAGIX VEGAS Pro (13.0 build 543 and later) simultaneously on 2 devices."
How do they check it's not your uncle (or whoever) that's using MAGIX VEGAS simultaneously?
And the OP please note that v 14 is MAGIX VEGAS Pro 14, not Sony any more.
The Purchase consultation contact links are towards the end of this page.