If you wouldn't mind some stupid startup questions I would like advice on how to checkout code for read only under windows 7.

Sure, but lets do this on the mailing list so everyone can see. I'm copying it now.

You'll need mercurial, which is the source code management tool I use:

http://mercurial.selenic.com/

There are some pointers to helpful documentation regarding how to use it effectively.

http://chirp.danplanet.com/projects/chirp/wiki/Developers

That page also provides a pointer to the repository. The folks on this list are also good resources.

Is there any thought about supporting USB since most newer radio interfaces seem to prefer that approach.

I'm not sure what you mean exactly. Almost all of the radios speak only RS-232, which means you need a USB-to-serial adapter to interface with them. Since these devices present themselves as virtual serial ports on all major operating systems, there is no additional work for CHIRP to do in order to support them.

The one exception I know of is the Kenwood TH-D72, which has a USB port on the device itself. However, just like all the rest, it presents itself as a USB-to-serial device, and thus behaves like everything else.

If I've completely missed your question, feel free to clarify :)

Thanks!