"While the Linux kernel and the associated open source
components that make up a typical Linux distribution are licensed
under open source licenses, those licenses aren't always sufficient
for contributions. Open source licenses in the view of some work
well for the consumption and distribution of open source, not
necessarily for contributions to open source.
That's where Project Harmony comes into play. Over the years,
the issue of Contributor License Agreements has been a thorny one.
Open source projects, contributors, lawyers and open source
advocates all have seemingly different views on whether or not
contributor licenses are really needed, and if so, what verbiage
they should include.