For tarball releases of HarfBuzz, look here. At the same place you will also find Win32 binary bundles that include libharfbuzz DLL, hb-view.exe, hb-shape.exe, and all dependencies.

The canonical source tree is available here. Also available on github.

The API that comes with hb.h will not change incompatibly. Other, peripheral, headers are more likely to go through minor modifications, but again, will do our best to never change API in an incompatible way. We will never break the ABI.

If you are not sure whether Pango or HarfBuzz is right for you, read this.