All content posted on this site is covered by licences specified by StackExchange (currently free CC BY-SA 4.0). However, code remains copyright its original authors.
The above statement also applies to any independently copyrightable modifications of others' code, where permitted under the terms of the original licence. It does not, however, apply generally to code adapted from others' answers on these sites, since that is only guaranteed to be available under CC BY-SA 4.0.
Please also see my answer in the standard relicensing thread on Meta TeX SE.
Note that I would prefer my code to be reused under the terms of the LPPL.