The licensing of gpg.vs has come to my attention.  It's GPL v2, so is
compatible with this viewer.  However, for the purposes of adding OTR to
V3 based viewers, where LGPL is needed, this might be a problem.

The actual gpg.vs code does not state any sort of license, but it
includes parts of other projects that state LGPL 2.1.  Only on
sourceforge does it state GPL 2.0.  There's been no activity since 2009
there, and the authors web site no longer exists.  The relevant parts of
gpg.vs are only Windows build tool wrappers, and thus it's not important
to consider their license for the purposes of linking, only for the
purposes of source distribution.  Certainly the actual Windows build
tools are not LGPL compatible.  Still, it might be worth it to try to
contact Francesco Picasso if GPL is a worry.  My guess is that Francesco
Picasso was simply not worried about the license.

Personally I'd be inclined to just rewrite the build tool wrappers as
cmake stuff just to make it more consistent with the rest.  Plus, V3
based viewers have their own LL invented method of dealing with the
problem of building external libraries.  V3 viewers might want to ditch
gpg.vs and just use that new autobuild tool.