The license includes a provision that restricts users from asserting their patent rights against AWS licensors. When AWS uses an open source project, the project becomes an AWS licensor. The author's concern may be that the provision could extend to the contirbutors... or employers of the contributors... and so on.

This is not just FUD:

> Amazon is using the provision to defend itself in a patent infringement case brought by Appistry Inc in US district court in Seattle.