"relatively simple graphics" that was funny.
Did you try to update tens or hundreds of textboxes or labels with as high as a few tens of Hz using the standard Windows GDI+ graphics?
And because you can design your own GUI you could place even thousands of DROs on the same screen.
It will just simply overload your computer with GDI+ and the worse is that it may work on some computers without too much overload and not on others.
OpenGL using hardware accelerated graphics which is basicly that you define a 3D space with your eye or camera looking at your scene from a defined point and view angle and orientation etc.
And then you place primitives like lines, triangles in your scene. You can also render them with images etc.
The UCCNC works like that, you just see the graphics flat and parallel of the screen because the camera and viewing angle and orientation and rotation etc. is setup so you see it like that...
OpenGL can render millions of lines and triangles and images on them without even loading your computer's CPU, because lots of things can be processed and happen directly on the graphics card.
You even have the freedom to decide several things to where and how to be processed.
And for the toolpath view you need OpenGL or DirectX anyways. And we decided OpenGL instead of DirectX, because it is platform independent in case if we will want to move to other OS platforms in the future.
So, using OpenGL is not at all an overkill for this type of application.
OpenAL is using the sound library built into OpenGL.
We used OpenAL to avoid the Windows-madness when sometimes Windows notifying you about sounds and showing you popups and icons on the taskbar about that the device or software wants to make sound etc.
With OpenAL this can be simply avoided.
And is why you need to install the proper OpenGL Windows drivers for your graphics card, because then Windows will know how to talk the OpenGL lanugage with your graphics card including how it can make OpenAL sound.