Looks like ChatGPT got it right with the description. Perhaps obvious, but the ".." check is to stop path traversal. Also, if you pass an additional arg, it takes that as a directory for the script to serve over http, defaults to CWD. The rest seems like enough explanation.
You can also pretty print gawk source with -o[filename], using - as the filename to print to stdout, so you can just run the oneliner version, but lead with "gawk -o- " and it will print the pretty version.
Edit: Also, the performance is terrible. Gawk's listen sockets suck because you get no granular control over listen/accept. The socat based one I replied to is probably much better.
You can also pretty print gawk source with -o[filename], using - as the filename to print to stdout, so you can just run the oneliner version, but lead with "gawk -o- " and it will print the pretty version.
Edit: Also, the performance is terrible. Gawk's listen sockets suck because you get no granular control over listen/accept. The socat based one I replied to is probably much better.