Mike Krol's GreMir models were wonderful. They were downloadable versions of excellent Polish models for which Mike had permission to send as downloads.
Tax law changes drove him out of business:
GreMir Models
The models were protected by a two-step process. After purchasing and downloading the model, you could look at all the instructions and images, but not the actual parts. You sent a message to GreMir and received downloaded software specific to the model that allowed you to view and print the parts.
Another great feature was that the software allowed you to print the parts at any scale simply by plugging in "48," "72," or whatever.
Mike is a genuinely nice guy who used to go to great lengths to help with any problems with the software. I can verify that he is a man of infinite patience, which I tested many times.
Don