I think you need to go see a qualified lawyer on this one.
In the title you wrote "open-source software providers" (my emphasis), this sounds as someone who gives away the software for free, but makes money on commercial support, consulting etc associated with the software. I'm not at all sure that would be considered "non-commercial" in court.
Wikipedia has a nice article on the subject. In the first paragraph it seems to hint at different countries having different laws regarding non-commercial infringement.
Lastly, some of the good open source licenses, like IBM's "Eclipse Foundation CPL" cover patents in detail. This would seem to indicate that patents are a concern with open source software; perhaps not for the creator but more for some of the smartest users.
So all in all, I think this issue is sufficiently complicated to require a visit to a lawyer specialized in patent law.