Hi, old libdmtx homepage (http://www.libdmtx.org/) is no longer available (Error 503), though sourceforge one is: http://libdmtx.sourceforge.net/ Please update.
Thanks, fixed in git. https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=37396750b465f29044034cb4683e6dedd793ee36