FOSS is an inclusive term that covers both free software and open-source software, which despite describing similar development models, have differing cultures and philosophies. Free software is the term used and strongly recommended by the Free Software Foundation and refers to the users’ freedom to copy and re-use the software. The term “open source” software was developed and promoted in the late 1990s to clarify the main goal of software being available for modification instead of being available without costs. In short, free software focuses on the fundamental freedoms it gives to users, whereas open source software focuses on the perceived strengths of its peer-to-peer development model. FOSS is a term that refers to both without particular bias towards either political approach and is used in contrast to proprietary software, where the software is under restrictive copyright and the source code is usually hidden from the users.
The definition of Free Software can be found at the Free Software Foundation and the definition of Open Source Software can be found at the Open Source Initiative. One of our partners, the Institute for Legal Questions on Free and Open Source Software (ifrOSS), provides a nice overview of various different free and open source licenses. They have also published a comprehensive set of FAQ. Relevant news and interesting articles on free and open source software can be found at lwn.net or opensource.com.