When I was active on ServerFault I was quite vocal about my objection to licensing questions not being allowed. Despite this I followed the rules and voted to close such questions, because that was the agreed thing to do here on SF, it felt wrong to me, but I went with it, as the rules are driven by the community. I remember suggesting at the time that I'd write about why I thought licensing questions should be allowed, so here goes...
Disclaimer: In my experience 'Vendor' in terms of licensing is synonymous with 'Microsoft', other vendors are available, etc, etc.
I'm going ask a couple of questions here to demonstrate a point
Should licensing questions be closed?
What's the worst that's going to happen if you follow bad advise and get it wrong?
If you're trying to do the right thing with a licensing issue (you are, because you're asking about it), then if you get it wrong, the vendor isn't going to be hitting you with legal action, they're going to help you put things right. Sure if you want to be 100% certain, then contact the vendor and do as they tell you, that way you're covered, but if you do follow bad advise from SF and get it wrong and are caught out, it's not the worst thing ever as many here on SF seem to think. You might have to explain to your boss why you're having to spend money on extra licenses that you hadn't allowed for, but the chances of actually getting into legal trouble is pretty slim, unless you're actually trying to circumvent purchasing licenses, or pretending you don't have licensing issues when you know you have them (to the point where you are not cooperating with vendors interested in auditing you).
Should technical questions be closed?
What the worst thing that's going to happen if you follow bad advise and get it wrong?
If you're trying to do the right thing with a technical issue (you are, because you're asking about it), then if you get it wrong, you could end up losing some or all of your company's data. You might have followed advise that resulted in no backups being taken in the last few years, worse still, both of the above. The chances of losing your job are almost certain, the chances of the company going out of business are high, and it's also likely you'll be held liable for damages for your conduct.
The definitive way of obtaining support in both the above situations is via your vendor (hey, I've just made ServerFault redundant with that statement!). You can write a really good question about a technical problem which details every aspect of the problem with a fanatical level of detail in the question, you get can many really good answers from the many knowledgeable people here on SF, the person responding might have had the exact same failure on the exact same hardware just the day before, but when following the offered advise you can still get it wrong. When the boss calls you to his office to explain yourself, given the choice of being able to respond with 'I followed the vendors instructions' or 'I asked on a public QA website for sys admins', you're always going to be in a better position if you can say that you sought advise from the vendor.
I believe many people don't want licensing questions being asked on SF, because they aren't technical questions. We're all geeks, we like technical questions over licensing questions any day of the week. Licensing is the boring part of systems administration that everybody wished they didn't have to deal with. It's a complicated subject, it's easy to get wrong, and not many people understand how it works, and it's easier to not have to think about it, so the consensus here is that it becomes a taboo subject, it's much easier to pretend it doesn't exist. In reality, licensing is essential for systems administration, you need to know this stuff, every time you deploy some software or install an operating system, you should ask yourself if your existing licenses cover you for this installation. If you don't, you aren't doing your job properly. Licensing is hard, but much like a technical issue you might find yourself battling with, once you spend some time researching it and seeking advise, it's actually not that hard.
Given that the implications of getting a licensing issue wrong are far less than getting a technical question wrong, software licensing questions should be allowed long after technical questions are no longer permitted on SF.