If you want to access and compile the latest source code from the SVN repository on Windows I suggest using [http://www.microsoft.com/express/vc/ Microsoft Visual C++ Express] and [http://tortoisesvn.tigris.org/ Tortoise SVN].
For connecting to the SVN repository you can follow the [http://code.google.com/p/heron-language/source/checkout instructions here].
If you just want to browse the source online [http://code.google.com/p/heron-language/source/browse/trunk go here].