Opo is software to show synchronised video on multiple monitors or projections. It can show four 1024x768 projections on a cheap computer, and probably more with more expensive hardware.
Opo was written for use in art galleries (originally, for LeiLani Kake's Ngā Hau e Whā at Fresh Gallery Otara), and is designed to start up automatically when the computer is switched on. It comes with an optional GUI to assist with the compilation and selection of sets of video, but you don’t need to use that. There are also example configuration files for running it with the xorg radeon driver. Whether it works with other drivers, or with operating systems other than Linux, is an open question.
Opo is free software, available under the terms of the GPL version 3. It is written in C and based on Gstreamer and GTK. The GUI front end is written in Python, using GTK.
To install it, get the source from this git repository and read the README.