Actually it looks like the issues I'm seeing on OS X have nothing at all to do with the endianness. Content-length seems to be incorrect here for some reason. Investigating now. If anyone else is trying to run pushpool on OS X, please drop me a note. Would love to compare notes / sanity check.
Update: the problem had to do with strndup on OS X. Fixed and pushed to my fork at http://github.com/zapnap/pushpool. If someone else is using OS X I'd love to hear from you .