Sources at home link are not here now (error 404 from hosting). Backend, pmount, last updated in 2012 (in bzr), releases in portage are versioned as alpha. As far as I understand , pmount was first way to mount/unmount removables without root, but now this problem looks solved everywhere.
There are at least two active alternatives - mount-gtk and udiskie, both using udisks, with support for gtk3 and probably wayland.
