Another factor not addressed by the Stack Exchange answers is that even where the poster had the legal rights to post the code, it may not be under the licence

Another factor not addressed by the Stack Exchange answers is that even where the poster had the legal rights to post the code, it may not be under the licence that Stack Overflow says it is. Stack Exchange retroactively "changed" the licence from CC-BY-SA 2.5 to 3.0 in 2011,[1] and from 3.0 to 4.0 in 2018,[2] without getting permission from the people who own the rights. So the code actually remains under the original licence. If the code is used verbatim, it must be released under the same version of the CC-BY-SA licence (unless permitted by the copyright holder), but adapting it would let you put the new work under a later version.[3] But there is also a jurisdiction-dependent question of what constitutes an adaptation, and how much of the larger codebase could be considered an adaptation of the CC'd work (and would therefore be covered by the same licence).[4] 1. https://meta.stackexchange.com/questions/74867/should-stack-exchange-switch-to-cc-by-sa-3-0/95033#95033 https://meta.stackexchange.com/questions/74867/should-stack-... 2. https://meta.stackexchange.com/questions/333089/stack-exchange-and-stack-overflow-have-moved-to-cc-by-sa-4-0/333094#333094 https://meta.stackexchange.com/questions/333089/stack-exchan... 3. https://opensource.stackexchange.com/questions/7430/can-i-upgrade-the-version-of-cc-by-sa-from-3-0-to-4-0-in-my-modification/7431#7431 https://opensource.stackexchange.com/questions/7430/can-i-up... 4. https://wiki.creativecommons.org/index.php?title=ShareAlike_interpretation&oldid=100807#Examples https://wiki.creativecommons.org/index.php?title=ShareAlike_...