How does that work with their patent threats? Eg against mono, gnome, tomtom(?) for using a Free implementation of the fat filesystem? I haven't been following

How does that work with their patent threats? Eg against mono, gnome, tomtom(?) for using a Free implementation of the fat filesystem? I haven't been following it but is all that renounced so it can't possibly come back or be applied to the next people? My first reaction is "How do we know that releasing the code isn't just bait?"