Speex is available under the terms of the Xiph.Org variant of the BSD license, which is both an open source and free software license. Since there’s some confusion as to what this actually means to current and potential users of Speex, this page exists to clear up any misunderstandings.
A program is free software per the Free Software Definition) if its users may:
A program is open source if its license complies with the Open Source Definition, which, unlike the Free Software Definition, is a bit long to be copied here. Most popular free software licenses are open source licenses, and vice versa.
There are many licenses that qualify as free software licenses, and the Xiph.Org variant of the BSD license is one of them. However, some people prefer to release free software under a license that copylefts the work, which ensures that all derivative works of the copylefted program are also copylefted free software programs. The GNU GPL is one popular copyleft free software/open source license.
The Xiph.Org variant of the BSD license is
not a copyleft license.
This means that you can integrate it in proprietary programs, without
having to release your source code, or anything else.