An Acronym with multiple meanings:

• OpenSource Software
• OpenSource Society, à la NZOSS
• Open Sound System: the older Linux sound architecture, being phased out in favour of ALSA.

OSS is also a commercial system for audio drivers for Unix, written by 4Front Technologies (http://www.opensound.com). There is a GPL implementation of the OSS libraries as well as drivers for many sound cards. (This is called OSS/Free and was originally contributed to by 4Front. Their website says "There is no affiliation between OSS/Free and OSS/Linux anymore except that they are both OSS compatible."). These GPL'd drivers are in the LinuxKernel (2.0 and later).

In recent news 4Front have announced that their version of OSS will be released under the GPL for Linux and BSD and the CDDL for Solaris