Who uses Signed-off-by and DCO?

git provides options and configuration variables to easily handle the Signed-off-by tag line. It is used to certify that the sender certifies the patch with the Developer's Certificate of Origin.

I have read SubmittingPatches document and understand this convention is used by the Linux Kernel Project.

I was giving a git introduction to students in my lab, and this question came up from one of them. How widely is this convention used? Are there projects other than the Linux Kernel and git itself?