Install via the Ebuild in Gentoo's Portage
Gentoo's Portage currently has version 1.10.4 of uGet.
Install the aria2 Plugin
Gentoo's Portage currently has version 1.30.0 of aria2.
Gentoo is a Linux distribution that is designed to compile packages from source at the time of installation instead of using binaries for ultimate control so there are not any prebuilt packages available.