Have you sold licenses ViArt Shop Free, ViArt Shop Light, ViArt Shop Standard, ViArt Shop Enterprise.
Is there a file-difference between these licenses?
There is absolutely no difference in files between these versions, all of them use the same archive available here:
http://www.viart.com/Free_Evaluation_Download
The license file is what makes these products different.
Can I customize a free version and then purchase a license ViArt Shop Light.
Why not.
Can I pick upgrade after an unspecified period of licenses to Light Standard?
If you mean that after certain period of time, let's say 2 years, you wish to upgrade from Light edition to Standard edition -- yes you can via this page:
http://www.viart.com/upgrade_version.html
But please do not forget that by upgrading product edition you don't automatically receive free version updates, it needs to be purchased separately at
http://www.viart.com/updates_extension.html
So in our example, after 2 years you can continue using the same version (v.4.0.5 for example) and upgrade to Standard edition with the help of
http://www.viart.com/upgrade_version.html
But if you wish to use new version along with your Standard edition (for example, v.4.1) you'll need to buy both:
http://www.viart.com/upgrade_version.html
and
http://www.viart.com/updates_extension.html
Regards,
ViArt Team