Note: I'm using the term »Software« for plugins & themes.
Sadly we've lots of Qs like this one which ask for support for commercial »Software«. Most paid »Software« has support included or at a low per month rate.
Out FAQs currently don't deny the support for such »Software«. IMHO that's not ok. If someone is developing »Software« and making her/his daily live from it and invests lots of time to keep the »Software« living, then they should've the chance. @Wyck summed it up pretty well.
I know, that some/most of this »Software« is Open Source, but without a public source, we're unable to help and from a moral point of view I'm not able to help too.
I'd go even one step further: We should state in our FAQ, that we're allowed to report every user to the »Software« author (as long as we got some sort of contact data). 1)
I want WPSE to be a source for Open Source »Software«, but I also want it to respect the work and live of other plugin authors.
Another BIG issue for supporting such Qs also is that the source in most cases isn't available publicly. So how would we offer support for something where we don't know what happens under the hood?
This edit is only here as it seemed to be not've been written clear enough in the ↑ paragraph.
1) That's my personal opinion and should've maybe been part of an answer. I don't want finger pointing discussions, so I striked it out.