I know he is responsible for a lot of the great lore that makes up the TES Universe, but I'm wondering:
Some of the discussions here that revolve around info coming from MK, seem to include info that wasn't present in any of the games, but rather presented by MK in his " free time"?
Is this correct? And if so, does the lore community actually consider this info as real/canon?

Well, all of Kirkbride's work is certainly quite [numinit].

Most people consider it semi-canon. MK keeps in touch with Bethesda, and Skyrim took alot of his obscure stuff (kalpas, Alduin being shed from Aka, Ysgramorf) and put it in.

There seem to be three views on this.

1. If it's not in the games (or outside souces explicitly endorsed by Bethesda, like the Keyes novesl) it's not canon. End of story.
2. MK's stuff is canon, because it's MK. End of story.
3. Who cares about what's canon and what's not? We like MK.

Numinatus! is most definitely canon.

Ysgramorf? Is that just a typo or is there some manner of silliness going on with Ysgramor?

Good ole Heimskr has essentially canonized MK's attempt to retcon why Cyrodiil was a jungle in Oblivion.

And the Thalmor's activities fit in real well with the "Altmeri Commentary on Talos".

Doing a search for canon or MK or amadeus will bring up countless discussions about this.

General idea is that while he isn't officially a dev, he does still write things for Bethesda(Pelinal stuff, commentaries, etc) and there have been nods to his more recent work in Skyrim(the painted cow).

Also, we know Beth plans ahead(they thought up the basic ideas for all the games up to Skyrim right after Daggerfall), so MK probably knows where things are headed, even if he doesn't know specifics.

And if we disregarded MK's stuff we'd just be talking about elven lifespans ands half-races all day.

Typo. But I like it!

I understand if you want to keep some of MK's more novel contributions on limbo.

But if you don't read it, and read carefully, you will never have a prayer of understanding the most important concepts in lore, most of them heavily involved with the plots of the games themselves. Lots of the so-called obscure texts are absolutely vital for explaining and completing the in-game lore, and there is a lot of cross-fertilization between what MK does 'in his free time' and what Bethesda ships on disk.

In general, we don't care about canon. TES lore is a work of fiction, and fiction belongs to its authors, not the authors estate or whoever bears the copyright.

Source? It's not that I don't believe you, it's that this is a cool concept and I'd like to read more on it.

Yes, I understand that plenty of his stuff is very good to fill in the gaps of the ingame lore and to help you understand. But there are some things, like this whole CHIM thing which I started noticing here on the forums not too long ago... and some other things that I can't remember anymore, that just seem too... weird to ever be considered canon/appear in a game.

Though, like I said, several things does fit nicely with the canon lore!