"In spring 1991 the dongle protection scheme of EAGLE 2.0 had been cracked causing a decline of 30% in sales, while sales for a reduced demo version with a printed manual saw a significant increase.[4] As a consequence in 1992 CadSoft sent thousands of floppy disks containing a new demo of EAGLE 2.6 to potential users, in particular those who had ordered the former demo but had not subsequently bought the full product.[4] The new demo, however, also contained spy code scanning the user's hard disk for illegal copies of EAGLE.[4] If the program found traces of such, it would show a message indicating that the user was entitled to order a free printed manual using the displayed special order code, which, however, was actually a number encoding the evidence found on the user's machine.[4] Users sending in the filled out form would receive a reply from CadSoft's attorneys.[4][33] The act of spying, however, was illegal as well by German law.[4][33]"
Sheesh. I just remember later versions having a pretty astute anti-piracy scheme where newer versions had some kind of blacklist of pirated keys, with the key stored in the binary save file - files produced by a pirated copy couldn't be loaded by a newer version. There were pretty great tools for textual import/export though, so it was relatively easy to work around.
"In spring 1991 the dongle protection scheme of EAGLE 2.0 had been cracked causing a decline of 30% in sales, while sales for a reduced demo version with a printed manual saw a significant increase.[4] As a consequence in 1992 CadSoft sent thousands of floppy disks containing a new demo of EAGLE 2.6 to potential users, in particular those who had ordered the former demo but had not subsequently bought the full product.[4] The new demo, however, also contained spy code scanning the user's hard disk for illegal copies of EAGLE.[4] If the program found traces of such, it would show a message indicating that the user was entitled to order a free printed manual using the displayed special order code, which, however, was actually a number encoding the evidence found on the user's machine.[4] Users sending in the filled out form would receive a reply from CadSoft's attorneys.[4][33] The act of spying, however, was illegal as well by German law.[4][33]"
https://en.m.wikipedia.org/wiki/EAGLE_(program)#Controversie...