UPDATED JULY 17, 2019

To keep this tag clean and meaningful, please ensure your post fits into at least one of the following categories:

• Organizing, managing, running, or working in an Open Source project.

• Open Source philosophy, licensing, and/or practical and legal topics thereof.

• Advocacy and adoption of Open Source technology.

DO NOT use this tag if you are simply using a technology which happens to be open source.

You should NOT use this tag for any of the following:

• Promoting an open source project, such as feature lists or announcements. (Use Listings.)

• Contributor requests. (Use Listings.)

• Tutorials/articles that happen to use an open source tool. (Use appropriate technology tags.)

• Showing off something you've build that HAPPENS to be open source. (Use the #showdev tag.)

Projects must comply with the Open Source Definition (see below) to legally use the term "open source".

As all "Free Software" officially complies with the standards of Open Source anyway, this tag covers both (collectively, FOSS).

Open Source is so much more than "you can read the code". It is formally defined by the Open Source Initiative.

"Open Source" should not be confused with the similar Free Software, which is defined by the Free Software Foundation. Generally, all Free Software is also Open Source, and the two camps often cooperate; however, the concepts are distinct! (The tags are merged here on DEV.to for simplicity, however.)

Open Source Hardware is defined and overseen by the Open Source Hardware Assocation