Antivirus license

[Tomàs Núñez Lirola <tomas@asertel.es>]

Hi
I want to put an antivirus on the mail server (BugBear helped me to convince 
my boss). Now is time for wondering about licenses.

Kaspersky and F-Prot (two examples) have a product for a mail server. If I use 
their product for a personal use (wich license price is a 5% of the mail 
server license) with amavis, am I doing something illegal? Does the license 
permit its use with amavis?
I need to know it for sure... so can anyone help me?

However, the open alternatives (clamav, openantivirus, etc) are stable enough? 
They get updated fast enough?