MinGW - Minimal SYStem
MSYS was conceived out of a long-lived desire to provide the MinGW community with a Minimal SYStem, offering a Bourne Shell command line interpreter environment, which would be capable of executing POSIX style configure scripts, and of interpreting the ensuing Makefiles, in order to build typical Open Source projects, while requiring minimal changes, if any, to their build systems. It is available from the MinGW download area on SourceForge.
MSYS versions 1.0.8 and later include only the i386 binary distribution, which will run on any 32-bit Intel-compatible processor. The tarball flagged as "src" contains the source code for MSYS runtime and each package used to provide executable binaries, which is unnecessary unless a manual build is desired. Source tarballs may not be provided for snapshots and prereleases, so the latest source should be obtained from the "msys/rt" and "msys/packages" modules in MinGW CVS. The files ending in "odmp" and "perdr" are used to diagnose the a stackdump should that occur.
More information about using MinGW with MSYS can be found in the FAQ, and the current MSYS documentation can be found in the "\msys\1.0\doc\msys" subdirectory within the binary distribution.
There is also a mailing list for MSYS discussion (MinGW-msys). See the Mailing Lists page for more information and access to this list.