I've done this myself by examining his nwncx plugin for bypassing the master server.
IntPtr i2 = new IntPtr((uint)m.ProcessHeld.MainWindowHandle + 0x004D4AF7);
byte[] b = { 0x84, 0xF2, 0x06 };
m.WriteByteArray(m.ProcessHeld.Handle, i2, b);
You need to find the memory location at 0x004D4AF7 within nwmain.exe
Write 84 F2 06 to that location and voila
When the gamespy password prompt appears, you can enter anything you want, and it will skip the master server validation.