I'm following up on Sven's comment in
http://lists.wfu.edu/pipermail/gretl-devel/2014-October/005328.html
('join' with gdt files).
There's now something new for testing in CVS: you can use "join" with
gdt (or gdtb) files as well as CSV. There may be a few rough edges,
and the documentation is not yet updated.
Allin