From LXF Wiki
SDL, which stands for Simple DirectMedia Layer, is a portable C/C++ library which creates a simplistic set of functions for manipulating display, audio and input devices. SDL supports a number of platforms including; Linux (x86, Sparc, PPC, Alpha), Solaris (Sparc), Win32 (95, 98, NT), BeOS (x86), and MacOS (PPC). The SDL library is most often used for games, where advanced constructs such as resizeable windows, menus and such aren't often a primary requirement. SDL was originally developed by Loki Entertainment Software (or just 'Loki') under the LGPL and is now an independant project.
For more information on SDL see  (http://www.libSDL.org)