http-parser is based on parsers from mongrel and/or nginx (at least in parts), yet the LICENSE file says Joyent, Inc. and other Node contributors.... No mention of the original copyright holders (Zed Shaw and/or Igor Sysoev) tsktsk
There isn't a shred of the original mongrel parser left. I'm not 100% sure but http-parser looks more like it's inspired by nginx than that it actually contains nginx code.
Disclosure: I know both http-parser and nginx fairly well. I'm one of the 'other Node contributors'. :-)