Hi Hugo,
Thanks for your work on msgpack, it seems like an interesting project. Unfortunately, machine floating point formats are complicated, so any related code will be complicated as well. I don't know much about the msgpack protocol, but if representing floating-point numbers as strings is an option, I encourage you to look at fpio (
http://wiki.call-cc.org/eggref/4/fpio ), a BSD-licensed egg for converting floating point numbers to strings and vice versa. endian-blob includes code from GDB, so it cannot be relicensed without approval from the GNU project.