Free (Libre) and Open Source Software
Not to be confused with #dic:freeware
FOSS or FLOSS is a combination of the terms Free or Free/Libre Software and Open Source Software.
The terms are very similar as they both talk about software that can freely be used, studied, altered, shared and redistributed, but there is a fundamental difference in the philosophy behind the two terms.
Free (Libre) Software
The Free Software Foundation defines Free Software as software that respects its users Freedoms. Free Software is controlled by the user while proprietary or non-free software may control the user by reporting his activities or restricting his access to information.
Open Source Software
The Open Source Movement is a spin-off of the Free Software Movement. Originally they proposed the term Open Source instead of Free so it wouldn’t be confused with #dic:freeware , but since the word “open” doesn’t imply anything about Freedom the Open Source Movement moved away from putting Freedoms on top and rather emphasize the practicability of non-proprietary software.
See also:
Free Software Donation Day