emerge -pv google-talkplugin
/usr/portage/licenses. To get a specific license try
ls /usr/portage/licenses | grep google
/etc/portage/package.licenseto reflect it. In this case, the line would be
<full package name>
/usr/portage/distfiles. The problem is Google provides you current version and not the version considered stable by Gentoo. Moreover, the version 1.8 which is considered stable by Gentoo is not available according a Gentoo bug [I wish I had found that out earlier].
distfilesfolder and portage will not have any checksum error either if the versions have not changed.
cp -v Downloads/google-talkplugin_current_amd64.deb /usr/portage/distfiles/google-talkplugin_188.8.131.52-1_amd64.deb