zgen is described as 'A lightweight plugin manager for Zsh inspired by Antigen. Keep your .zshrc clean and simple' and is an app in the OS & Utilities category. There are five alternatives to zgen for a variety of platforms, including Linux, Mac, zsh, BSD and Windows. The best alternative is Oh My Zsh, which is both free and Open Source. Other great apps like zgen are Antigen (Free, Open Source), Oh My Fish (Free, Open Source), Prezto (Free, Open Source) and zplug (Free, Open Source).
Antigen is a small set of functions that help you easily manage your shell (zsh) plugins, called bundles. The concept is pretty much the same as bundles in a typical vim+pathogen setup. Antigen is to zsh, what Vundle is to vim.