https://bugzilla.redhat.com/show_bug.cgi?id=1150393
--- Comment #4 from Jan Kaluža jkaluza@redhat.com --- Tengine is fork of nginx. The nginx code is patched heavily to bring new features. Upstream merges changes done by nginx upstream into Tengine when new nginx version is released.
It's the same situation as for MySQL vs. MariaDB. I don't see any bundling exception for MySQL vs. MariaDB.