Jacobsen wrote some software to let you connect your computer to your model railroad and control trains. He made the source code available and gave away the software for free.
KAM Industries, maker of commercial software that does something similar sent him a letter claiming that the software infringes its patent.
When Jacobson asked them how, the outfit sent him a bill for $203,000 claiming that more than 7,000 people had downloaded Ben's software and since it was really KAMs he should pay at least $29 for each of them.
Not satisfied with that, KAM sent a request to the author's academic sponsor requesting copies of all his email and other correspondence.
After several more threatening letters, Jacobsen said that he didn't believe the KAM patent would withstand a challenge in court.
He said the software was written long before KAM filed its patent application and the outfit must have known this when it started sending its rude letters.
The case is still ongoing and is detailed here. ยต