One take-away from this is this, though: When it comes to patents - the fact that your software is non-commercial, or that you invented it independently withou

One take-away from this is this, though: When it comes to patents - the fact that your software is non-commercial, or that you invented it independently without knowing about the patents does not matter. Unless you can prove you created the infringing work before the original patent applicants did, in which case you can invalidate and/or take over the patent, patent rights are fairly absolute, and have nothing to do with derivative works or anything like that (which is why software patents suck so much....) Patents are granted via application, and apply unilaterally, regardless of how the infringing works were created. The only defences in general against patent infringement are a)your product does not actually infringe on the patent because it's different enough and b)attacking the validity of the patent itself. Contrast with Copyright, which is granted automatically, and independent creation of similar works (even identical) is permissible, as long as they were truly independent and not copying each other. (This is why clean-room reverse-engineering techniques, where one group revere engineers the software and documents it's function, and a completely separate group who's never seen the original work writes new code to those specifications) work for software when it comes to copyright, but not against patents.