Bettercap is an open source project licensed under the GPL3 License. This means that you can use, modify and adapt it to your own needs.
Bettercap was designed to be fully modular, wether you are a developer or a security researcher it will be really easy to write your own customized proxy module.
No need to compile anything, just fire up your RubyGems environment and run bettercap on GNU/Linux, Mac OS X and BSD.
One single tool with everything you need to perform a MITM attack, traffic redirection, credentials harvesting, HTTP(S) injection and more!