Anyone know of an API to detect control properties from an executable without looking at the source code?

I ask because I found an online decompiler that returned the form and control properties of an exe and I'm trying to determine if that means that it could generate source.

We bought an app from a VAR. The customization tools that came with it are very limited. I just want to modify it for our own use -- not for resale to others.

Thanks for any help,
Wade