Are the 3.5e Dragonlance books third party or official works?

When 3rd edition rolled around, Wizards of the Coast handed the maintenance of the Dragonlance setting to Sovereign Press, the printing company owned by Dragonlance co-founder Margaret Weis. They released several Dragonlance books all the way until the end of their licence, not too long before 4th Edition came rolling around.

But I’m curious if this means that those Dragonlance books are canon. I rarely see them being referenced by guides and people talking about character builds in general, and even then in only a select few cases. which lead me to suspect that the books are not “official” works like the regular, the Forgotten Realms and the Eberron books are.

Is this true? Are they third party works because they’re printed by Sovereign Press rather than Wizards of the Coast? Or are they still official because Sovereign Press was licensed to print them, and they are an established setting and bear the WotC seal of approval?