The interface uses either the touch screen, or a directional pad and select button, with separate back, menu, and home buttons. It is capable of two modes of text input: handwriting recognition, and two different sizes of onscreen keyboard, as well as hardware keyboard input with the N810.
The UI in Maemo 4 is similar to many handheld interfaces, and features a "home" screen, which acts as a central point from which all applications and settings are accessed. The home screen is divided into areas for launching applications, a menu bar, and a large customisable area that can display information such as an RSS reader, Internet radio player, and Google search box.
Maemo is mostly based on open source code, and has been developed by Maemo Devices within Nokia in collaboration with many open source projects such as the Linux kernel, Debian, and GNOME. Maemo is based on Debian GNU/Linux and draws much of its GUI, frameworks, and libraries from the GNOME project. It uses the Matchbox window manager, and the GTK-based Hildon as its GUI and application framework.
It is not open source, though it contains some. Both to use the device or to develop through the maemo SDK (only way unless you stick to scripting languages already in the device), proprietary software from Nokia is mandatory.
Maemo is a software platform developed by the Maemo community for smartphones and Internet tablets. It is "based" on the Debian Linux distribution, but has no relation with it, especially for what concern open source.