9menu is described as 'create a menu to run commands' and is an app in the OS & Utilities category. There are more than 10 alternatives to 9menu for Linux, Windows and Mac. The best alternative is dmenu, which is both free and Open Source. Other great apps like 9menu are Zenity (Free, Open Source), Yad (Free, Open Source), KDialog (Free, Open Source) and whiptail (Free, Open Source).
Yad (yet another dialog) is a fork of Zenity with many improvements, such as custom buttons, additional dialogs, pop-up menu in notification icon and more. It's useful for creating quick and easy GUIs for shell and batch scripting.