Rubygame is a cross-platform multimedia library for the most wonderful programming language in the world: Ruby. It embraces the Ruby spirit to provide developers with a library that is simple and easy to use so you can get things done painlessly, yet powerful and flexible so you can get them done right.
Even though it's called Rubygame, it has uses far beyond just entertainment software. With Rubygame, you can create scientific data visualisations, educational/training tools, interactive motion graphics, and more.
Rubygame is open source, licensed under the GNU LGPL version 2.1 or later. That means you are free to use, copy, modify, and distribute it, even to make proprietary applications. (Read the full license for details, of course!)