Sadly this is true, when I worked at a software company the first thing
they said was: Don't look at patents. If you however still believe that
you infringe on one, only contact a lawyer, because the client attorney
conversations are confidential. Looking for software patents is just
asking for troubles. It's better to stay completely ignorant.
To the best of my knowledge, my current debian system infringes on zero
patents. :) .. and I'm not even going to look for anything that might
possibly infringe ..