Cygwin is a DLL which provides a Unix emulation environment for Windows. The Cygwin environment provides a complete port of such development utilities as gcc, binutils, gdb, make, etc., as well as a vast number of useful utilities.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.