I will start by offering the view that this question is off-topic. If code is sitting on github with no license, that means that it has no open source license. If there is no open source license, then we are simply discussing copyright law in general, not open source licensing in particular.
We've discussed general copyright questions before, and generally agreed that they're off-topic.
But that doesn't mean that every question must necessarily be about strictly FSF and OSI approved licensed projects. In fact it will often prove to be the questions which don't fit so easily into these boxes that are the most interesting, and for which this site will be most useful.
You can upload proprietary projects to Github, but the Terms of Service require you to allow other users a "right to fork". There's also the ability to clone etc. So questions about what the TOS means in terms of such a project's implied FLOSS status are a great fit for this site.
This site is called "open source". We are talking about open source software. And… it would be off-topic?
There are many definitions of open source, and I agree that a software that allow you to look at the source but do nothing with that is a bit useless, but it's still open source nonetheless.
(this, and what @curiousdannii said – I take he'll post it as an answer)