Good point, but apexskier/cryptoPadding doesn't have any license info, so it really shouldn't be used at all (importing, copying, or vendoring).
https://github.com/square/go-jose/commit/6722e7b8407c4b2bbe2...
Posting it to Github isn't implicit permission, but it would probably be a factor if the author did try to sue people for using his or her copyrighted work without license/permission.
[1] http://en.wikipedia.org/wiki/Open-source_software#Open_softw...
https://help.github.com/articles/open-source-licensing/#what...