MiKTeX is a) an implemenentation of TeX & Friends and b) a TeX distribution.
Please visit the MiKTeX project page, for more information.
This is the MiKTeX code tree. You use it to build the MiKTeX binaries.
Read README.unx, if you want to build for Unix system-alike (GNU Linux, Mac OS, Solaris, ...).
Read README.win, if you want to build for a Microsoft Windows system.