I'm struggling to understand this as well - I would have thought OSS licensing and software patents would be incompatible.
This is why the W3C has a patent policy [1] to prevent contributed software and specifications from being covered by patents.
[1]: http://www.w3.org/Consortium/Patent-Policy-20040205/
If this still does not make any sense, realize that patents and copyrights, while both forms of IP, are completely different, legally. Also recall how open source GIF implementations were still covered by the Unisys patent.