The Discourse code includes minified JS files with the MIT license. The minified versions of these files do not appear to include the MIT license directly, as that license requires. Of course, this is covered by discourse/COPYRIGHT.md at main · discourse/discourse · GitHub in the source. I think it would be a good thing to do to include this text somewhere on the standard about page, perhaps under a new “Licenses” or “Open Source Licenses” tab like FAQ and TOS.
I suppose it could also just go in the FAQ, but it seems like a good place to separately note that Discourse is open source and everything awesome about that.