IBM has donated 500 patents to open source (according to this 271 patent blog post).
Of course, the last time they donated a patent to the public domain, it was a real crappy one, namely, the infamous "System and method for providing reservations for restroom use" patent (USPN 6,329,919). Let me quote the abstract for you:
The present invention is an apparatus, system, and method for providing reservations for restroom use. In one embodiment, a passenger on an airplane may submit a reservation request to the system for restroom use. The reservation system determines when the request can be accommodated and notifies the passenger when a restroom becomes available. The system improves airline safety by minimizing the time passengers spent standing while an airplane is in flight.
Makes you wonder how crappy the latest 500 are.