The plugins are quite old Reproducible: Always
Since the plugins are downloaded automatically by JOSM, I suggest to remove the sci-geosciences/josm-plugins ebuild.
the favourite plugins are updated very frequently. (every one or few weeks) sci-geosciences/josm-plugins would help a user if a) the ebuilds are updated weekly, or b) if it would be at least an 9999 ebuild Both are not in sight and this bug had no attention for +1 year. I suggest to follow Jean-Claude Repetto and treeclean sci-geosciences/josm-plugins.
CCing treecleaners
# Dion Moult <moult@gentoo.org> (24 Sep 2015) # Masked for removal in 30 days. Bug #472002 # Can't keep up with upstream changes. sci-geosciences/josm-plugins
removed from the tree