OT: Using built-in ghostscript by itself

[Abraham Lee]

Devs,

I'm using Windows 7. I realize I can just download and install ghostscript
in the "normal" system location for what I want to do (which I've done),
but I was wondering if there's someone who understands the way that
LilyPond uses its built-in ghostscript command to do its job.

My question is this: How do I use the built-in ghostscript functionality by
itself?

I couldn't figure it out. When I call [LP_dir]/usr/bin/gs.exe I get the
error that it can't find gs_init.ps which is located in
[LP_dir]/usr/share/ghostscript/9.15/Resource/Init/. How do I tell gs.exe
where to find its files? Am I even using the right command?

Any help is welcome!

Best,
Abraham