kupfer is described as 'Kupfer is a command tool heavily inspired by Quicksilver ; you do not use it to search your files, you use it to summon an application or document quickly by typing the first parts of its name' and is a application launcher in the os & utilities category. There are more than 50 alternatives to kupfer for a variety of platforms, including Windows, Mac, Linux, File Explorer and Xfce apps. The best kupfer alternative is Listary, which is free. Other great apps like kupfer are Alfred, Launchy, Keypirinha and Wox Launcher.
Kupfer is Linux-only; Keypirinha is Windows-only.