not sure we're getting the whole story
Why would Siemens use password protected Excel files written by a third party and how come that third party kept the copyright ? What were the terms under which they were using the files ? ... this story is very strange
that guy must be a future seeing genius if he wrote Excel files which survived from the early 2000s until now with only his logic bombs preventing them to work
were they right after an Office upgrade when the files stopped working ?
my guess is the guy had a check to see if the file was not copied, and the rest of the failures were due to upgrades of Excel, and they sued him to get the IP and be rid of him
most DRM software works like code bombs anyway, I guess when it comes to going to jail it matters more if you're Johnny Public or BigCorp Inc.