For a specific example relating to my question, I offer VisIt.
Per the licensing information for VisIt, it is stated that it is BSD-licensed.
But, looking over the libraries used in VisIt, it can be seen for instance that Qt is used for VisIt's GUI. It is my understanding that Qt was never BSD-licensed, or, ever as unrestrictive as a BSD-license, and currently you can use Qt in terms of LGPL or commercial licensing.
As an aside, in the source distribution of VisIt, it includes the GPL and QPL license file for Qt, suggesting an even more restrictive license propagation setup, suggesting that VisIt should be released as GPL and not BSD, as it currently is. (I noticed in the About area in VisIt, they display the QPL license, but, as I understand it, that was dropped many Qt versions ago, and yet VisIt 'distributes' in both the source and binary sense, versions of Qt above v4 and v5.)
The reason I am asking such specific questions regarding VisIt is that I was going to utilize VisIt as the visualization component for a simulation program that I have written. Seeing as how it was BSD-licensed, I thought, 'great', but, in looking at the libraries that VisIt is utilizing, it makes me wonder how it could be BSD-licensed as a whole package. If it was for instance GPL-licensed, then I would not be using it in my 'potentially' commercial future for my simulation program.
So, in general then, does someone intending on using any given software (not written by you) in a commercial application have to scour the library dependencies for said software looking for a GPL-licensed piece of software that might 'force' you to GPL-license your application?