Mingw-w64 is an advancement of the original mingw.org project, created to support the GCC compiler on Windows systems. It has forked it in 2007 in order to provide support for 64 bits and new APIs. It has since then gained widespread use and distribution.
The development and community are very active and welcoming with new contributors every month and simple installers.
You can also look at the full list of versions.
Mingw-w64 interacts a lot with other projects in order to help everyone move forward. Contributions have been going to and coming from these projects:
Get partway down the package install list in the win-builds GUI and it just hangs with some package download failing, Installer will not resume - demands an empty folder to install, or exceptions-out. So there's no option but to keep on trying and fail again, on some (never the same) step or other. Making the installer more fault tolerant, retry-aware, would be good.
crt: Add a few more UUID's for IHTMLOMWindowServices etc
include: Add GUIDs for audio/image/media file summary information
crt: Add CLSID_DCOMAccessControl to uuid.c
crt: Add defines for IID_IEnumContextProps and IID_IContext in uuid.c
include: update winreg header file
crt: Implement IID_IAccessControl
widl: Updated to current Wine version.
headers: Regenerated imported headers with current widl version.
crt/urlmon: move to lib-common