UltraVNC

May I ask if there is a particular reason why the source code for the Virtual driver that works with UltraVNC is not open source, despite the UltraVNC is distributed under the GPL license?

Also, could you let me know if there is a document that you referred to when you made the Virtual driver?

I'm curious about how the Virtual Display works, so I attempted to understand the code for the UltraVNC Server.

Although I was able to locate the 'UVncVirtualDisplay.dll' file in the UltraVNC installer, I couldn't find its corresponding source code.

Where can I find this source code?

Thanks ...