Installation problem and a question

I'm running Vista x64 and while I can successfully install PG, I
can't seem to get PL/JAVA installed. The installer doesn't recognize
that I have a JRE installed (I do) and the option is grayed out
during installation.

So a couple of questions:

1) Should PL/JAVA be able to be installed on Vista x64 or is there
some known issue? What environment variables should be set, and how
should I set them for a JRE vs. JDK installation?

2) Where is the source code for the Windows installer? I've tried
fairly hard to find it, including Googling, browsing development
sites, and looking at the PG 8.2.4 source code directory, but no luck
so far. Sorry if this is a simple question but I don't know where
else to ask at this point. Among other things I wanted to look at how
the installer was detecting the existence of a JRE.