So, just to make things even less clear (because I'm interested in
seafile-server getting into debian)..
While Libzdb is currently licensed under GPLv3, it used to have a
exception
file allowing linking with GPLv2 code:
<https://bitbucket.org/tildeslash/libzdb/commits/dca8f99b12ebc1a1d6397744896e6ca9836591a4>
The db-wrapper code in seafile very clearly originated from libzdb, as
you've
pointed out. It's really not okay that they did that while stripping
out your
copyright and license.
However, the code that originated from libzdb seems to have come from
the
older version with the EXCEPTIONS file. I'm wondering if the way forward
here would be to ask the seafile folks to add your copyright info (as
well
as theirs), and the GPLv3 license to the db-wrapper code, and to also
include the GPLv2 exception file as well? Would that satisfy legal
constraints as far as shipping the GPLv3 code inside of a GPLv2
project in Debian?
