I have a dell e6540 and can only get blank screens. Works on open source driver only

DisplayLink calls out that the driver will not work with the closed source GPU drivers here -> You have to use the open source driver...

Why is it they can only support the propriatary driver in windows and not in Linux? I would like to use the hardware acceleration added.

Proprietary drivers for AMD/NVIDIA 

Closed source is not really the reason here, it's just the functionality of those drivers that we need. EVDI driver needs a DRM compatible driver for the main GPU, and uses the functionality provided by Xrandr 1.4 called offloading graphics display. This is a way for drivers to work together so that one graphics device can display images rendered by another. When we released the Linux driver, binary AMD and NVIDIA drivers could not be used like this out of the box. We need both the built-in GPU driver and EVDI to appear in the output of Code: