This question already has an answer here:
Has any specific policy about acceptability of links to Stack Overflow from third parties been adopted? How does the StackOverflow community feel about this kind of thing?
I came across this question: https://stackoverflow.com/questions/18080339/is-the-source-code-of-orbeon-forms-pe-professional-edition-available
My first thought about that product licensing question up front was: Why would someone not ask a vendor licensing question... to the vendor?
Then I found the answer: The vendor's site directs users with technical issues (that won't fit in a tweet) to post on StackOverflow: http://www.orbeon.com/community
IMO, this particular site, while not really outlining the details of what kinds of questions will be accepted on Stack Overflow, does an adequate job of instructing users on how to post (e.g. "phrase it as a question"; give a "minimal example"; "tag your question".)