CUPS was made in 1997, and was quickly used in Linux. Apple in 2002 started using CUPS, and in 2007 purchased CUPS.
It was originally made by Easy Software Products. As it was widely used in Linux before Apple started using it, I’m pretty sure it was always open source (their other major release was HTMLDOC which is also open source). Being open source before the purchase meant Apple had to keep it open source (but could guide where the official releases would aim).
This is a common misconception.
CUPS was made in 1997, and was quickly used in Linux. Apple in 2002 started using CUPS, and in 2007 purchased CUPS.
It was originally made by Easy Software Products. As it was widely used in Linux before Apple started using it, I’m pretty sure it was always open source (their other major release was HTMLDOC which is also open source). Being open source before the purchase meant Apple had to keep it open source (but could guide where the official releases would aim).
https://openprinting.github.io/cups/#HISTORY
It is now developed by Apple, but that was after the first 10 years of it’s development. This is why on the CUPS site (https://www.cups.org/) on the bottom it says “Copyright © 2007-2022 Apple Inc.”.
This has now been forked (by the maker of CUPS) into OpenPrinting CUPS.
Thanks for the correction!