About Free Software (quoted from Audacity website.)
OPI Console and SDK is free software, developed by a group of volunteers and distributed under the GNU General Public License (GPL).
Free software is not just free of cost (like "free beer"). It is free as in freedom (like "free speech"). Free software gives you the freedom to use a program, study how it works, improve it and share it with others. For more information, visit the Free Software Foundation.
Programs like OPI Console and SDK are also called open source software, because their source code is available for anyone to study or use. There are thousands of other free and open source programs, including the Firefox web browser, the OpenOffice.org office suite and entire Linux-based operating systems such as Ubuntu.
The GNU General Public License
The GNU General Public License is often called the GNU GPL for short; it is used by most GNU programs, and by more than half of all free software packages. The latest version is version 3.