MacHTTP is from Chuck Shotton of the University of Texas at Houston. From version 1.3 onwards, it is no longer free, though for private use it is not expensive. There is a 30 day free trial period for evaluation purposes - after that you have to pay. It runs on Quadras, PowerMacs and Mac IIs (the author has also tried it on a Powerbook 180 without any problems).
Installation of MacHTTP is extremely simple - it is supplied as a BinHexed Stuffit file. Stuffit is a common archive format on the Macintosh, and BinHex is a common Mac representation that enables binary files to be sent by email without corruption - decoders for both are freely available. Once it has been unstuffed it can simply be run with no additional configuration. For its more elaborate features, it makes use of Apple's AppleScript language, and the AppleScript extensions (which are covered under the license agreement and supplied with MacHTTP) must be installed.