Ok, executing that script on a machine would in most cases be totally legal. As long as this script was available to you by default, and you did nothing to escalt your privilages to get to it. However, your information is outdated, that script probally doesn't exist on most modern setups. I think it came installed as default on older Apache and NCSA Web servers. It gave you information about the files in the cgi-bin directory. Used mostly for information gather and exploit hunting...