YASAPI NT's 2.0.0-beta4 release consists of
* "out_yasapi-nt-2.0.0-beta4-msc.exe": the plug-in "out_yasapi-nt.dll"
compiled with a community edition of the Microsoft C compiler and
wrapped into an NSIS installer,
* "out_yasapi-nt-2.0.0-beta4-msc.7z": the plug-in "out_yasapi-nt.dll"
compiled with a community edition of the Microsoft C compiler and
packed into a 7z archive which has to be unpacked and the plug-in
copied to the directory "/Plugins",
* "out_yasapi-nt-2.0.0-beta4-gcc.exe": the plug-in "out_yasapi-nt.dll"
compiled with an MINGW edition of the GNU C compiler and wrapped into
an NSIS installer,
* "out_yasapi-nt-2.0.0-beta4-gcc.7z": the plug-in "out_yasapi-nt.dll"
compiled with an MINGW edition of the GNU C compiler and packed into
a 7z archive which has to be unpacked and the plug-in copied to the
directory "/Plugins",
* "out_yasapi-nt-2.0.0-beta4-src.tar.gz": the plug-in's source code,
* "README": this README file.
Beyond that you'll need a GTK runtime for Winamp you might download from
https://sourceforge.net/projects/yagtk-rt/files/