Cairodeskpane is a project mainly written in C, it's free.
Desktop Panes drawn with Cairo
This is the Cairo Desk Pane project, by Francis Whittle.
It's a desktop window divided into resizable panes into which you can put stuff, currently limited to terminals (provided by libvte). In the future more options will be available via a plug-in system.
Dependencies: Gtk+-3.0 VTE-2.90
Compile with gcc -o cairodeskpane $(pkg-config --libs --cflags gtk+-3.0 vte-2.90) *.c