The "unmet dep" is gambas-runtime >= 2.16 | gambas >= 2.16.
The latest version of gambas2 in the "normal" repos, testing included, is 2.15.
And it's gambas2, not gambas.
Seems it can be installed anyway, but I'm leaving it alone so I can test the working package.
(edit: removed stuff that belongs on gslapt thread)