I am writing a Blender add-on which enables the use of Blender with a piece of hardware (i.e., a lightfield display). Blender and the use of the specific Python API, which is required to write Blender add-ons, is licensed under GPL. In order to communicate with the lightfield display on the software level the manufacturer of the display provides a compiled, closed-source DLL under a non-GPL license. The add-on cannot provide the main functionality without this DLL.
No piece of third-party software can be written for this 3D display without this DLL. Since this DLL and the API calls it provides are fundamental to communicate with the display in general, me (and the manufacturer as well) consider this DLL to fall under the "system library exception" of GPL v3.
Issues / Questions
Assuming the copyright-owner of the closed-source DLL would grant me the right to distribute the DLL in its compiled form (.dll, .dylib, .so, etc.), while the DLL remains closed-source, non-GPL:
Is it GPL compliant to distribute this DLL within the add-on package or would GPL force me to let the user install this library? This question can be generalized to more general terms:
Is it GPL compliant to distribute any non-GPL, closed-source linked library, which falls under the system library exception, with GPL code?
While I would interpret GPL, that this is allowed, since I couldn't find any clause that prohibits distributing a system library in the GPL license, I couldn't find a reliable definite answer to this. I would appreciate if someone could answer my question and cite the corresponding text passage in GPL or any other official statement, from which the answer to my question can be clearly derived. Thanks!
Edit: There is also a passage in the GPL FAQs, which I would interpret in favor of my understanding, but I am not totally sure if I read it correctly. So any comments on this are welcome:
If the GPL-incompatible libraries you want to use meet the criteria for a system library, then you don't have to do anything special to use them; the requirement to distribute source code for the whole program does not include those libraries, even if you distribute a linked executable containing them. Source: https://www.gnu.org/licenses/gpl-faq.html#SystemLibraryException
Could someone confirm that this FAQ statement means that system libraries may be distributed with GPL code? And does this also count for non-compiled executables like Blender add-ons which are always distributed as python source code?