Gtkam (versions upto and including 0.1.9) install documentation into /usr/doc/gtkam. Specifically, it installs copies of INSTALL, COPYING, and MANUAL. Since the ebuild already installs copies of the same files into a version specific directory under /usr/share/doc, it seems unneccessary to have the files installed into /usr/doc/gtkam. I will attach a patch file that modifies the Makefile.in to remove the extra documentation install.
Created attachment 6425 [details, diff] gtkam-0.1.9-r1.diff
fixed in the tree, thanks for your patch. Sorry it took so long.