So, is it open-source or open source?
Missing from the pages of the Associated Press Stylebook is the correct use of the term open-source which until recently I had been using as just open source. Recently, an editor disagreed and though neither of us could find a definitive source, the editor always wins the ties. So, now I have to remember to write open-source for him, while I continue to write open source elsewhere.
The Open Source Initiative at opensource.org does not hyphenate the phrase open source.
Wikipedia goes back and forth between open source without a hyphen, and open-source with a hyphen, based pretty much on who the author was for that section.
The dictionary says, open-source with a hyphen.
There just isn’t enough evidence to force your way on whether open source has a hyphen or not. Do what your editor or client likes, and sleep well knowing either way is not a mistake.
Ah, the joys of writing 🙂
The 2020-2022 edition has a comprehensive entry on hyphenation in the punctuation section. The AP stylebook also calls out to the Webster’s New World College Dictionary 5th edition and directs readers/users to that volume for topics not explicitly explained in the AP stylebook. In that dictionary, it is hyphenated (I was dismayed to discover).