Notice that the entry is coloured brown, and it says that it is "source → portage → gentoo". Brown = not in Entropy. "source" = source code package, not binary package. "portage" = Portage, not Entropy. "gentoo" = Package ebuild in Gentoo's main Portage tree (if it had "sabayon" instead of "gentoo" then that would mean the package ebuild is in the Portage Sabayon overlay), i.e. it isn't in Entropy. In summary, each of those means it isn't in Entropy! File a request if you would like it to be added to Entropy:
Requesting Packages for Entropy - New Policy.