I am retired, no commercial use. I get the "Perhaps you didn't know..." pop-up maybe once a week. There is no way to tell it that I "DO" know the license terms and am abiding by them. I am not about to try the commercial version, even if it is a free trial.
Perhaps Avast! sees that I have more than 6 machines registered - that's because I play with virtual machines running various operating systems as part of my involvement in a user group, and chair a database special interest group. As part of the user group support I have a Windows Server 2008 installation which acts as a domain controller, SQL Server, as well as the VMware Server host for the virtual machines. As I just saw in someone else's post perhaps it is the presence of the domain server that is triggering the alert.
Note to Avast! - Servers don't necessarily imply commercial use.
And yes, it is the Avast! Free Antivirus 6.0.1289.
The point is - the 'nag' box doesn't provide a mechanism that allows me to confirm that I am legitimately using the free version. How about fixing that?