I know at least one big universe where the creator officially includes works that would ordinarily be considered fan fiction as canon (as in he actually took the best of fan fics, edited them, and on an on-going basis publishes them in-universe, AND had works in universe based on things in those fics). That example is from Alternate History - the 1632/Assiti Shards universe by Eric Flint.
Flint is a big time experiment builder in general (he seems to be one of the - if not the main - driving forces behind Baen's free library concept), so I was wondering whether the fanfic publishing concept is unique to him?
Question: Was Eric Flint unique in this regard?
Fan Fics here are defined as literary works produced by people who
have not been commissioned by a publishing house/owner associated with the universe
have not written their works with the expectation of being officially included in the universe (e.g. people writing a script with the goal of having Paramount shoot a Trek episode are not fan fic).
whose work was not directly requested by the owner/author of the universe.
crossover tributes by established authors by agreement with original owner don't count.
E.g. I'm looking for what anyone reasonable would genuinely consider an amateur fanfic.
As far as "considered canon", I am looking for indications of support by the owner of the intellectual property rights. This support can include republishing (with credit to the original fan fic source) with or without edits, or explicit references from the original author's works to events described entirely within fan fic sources coupled with statements by the author indicating that he/she made those references to the fan fic sources intentionally.