Welcome to the diStorm3 binary stream disassembler library project.
diStorm3 is really a decomposer, which means it takes an instruction and returns a binary structure which describes it rather than static text, which is great for advanced binary code analysis.
diStorm3 is super lightweight (~45KB), ultra fast and easy to use (a single API)!
"We benchmarked five popular open-source disassembly libraries and chose diStorm3, which had the best performance (and furthermore, has complete 64-bit support).", July 2014, Quoting David Williams-King in his Thesis about Binary Shuffling.
diStorm3.3 is now available for commercial use, http://ragestorm.net/distorm/.