Thank you for reporting. Actually, vendor/ is not correct indeed. This bug is recognized in upstream, so I'll follow in latest version later.
On Tue, 29 Sep 2015 16:55:56 +0200 Matthias Klose <d...@debian.org> wrote: > groonga ships third party software in vendor/ not mentioned in > debian/copyright. > > There is software in vendor/ which copyright is not the default. -- HAYASHI Kentaro <haya...@clear-code.com>