[Agrajag]

Don't forget that a nice portion of the Dominions III "DRM" is The Manual.
Aside from legalities, The Manual is a very good reason to choose a legal copy of Dominions III over a pirated one.
Selling Dominions III online would require either supplying the manual as a PDF (which would then be instantly pirated and spread through the internet, ruining the current "DRM"), or allowing a download and sending the manual by mail, which would actually be more expensive to do.