There is lots of stuff about software patents (see - here is one issue that has come up for me recently:

Extract from Contributors License

Without limiting the foregoing representation, Contributor represents that, 
to the actual knowledge of Contributor as of the date of this Agreement 
and without implication of a duty to investigate, the Submission in the form 
provided by Contributor hereunder will not violate any third party patent, 
trademark or trade secret right.

As software developers, we know that the main problem with software patents is, any source code of significant size will violate a number of patents. Finding out which is difficult. Paying for them is impossible.

Difficult issue?