Yeah I heard that too. I can't think of any specific movies (or TV shows) but I feel like I've heard his speeches (mostly the "I have a Dream" one of course) in other non-documentaries.

The MLK estate has been going through some turbulent times, with his kids fighting over who has the responsibility (and opportunity) of managing his legacy. It wouldn't surprise me if they allowed other films to use his words, but some familial power shift means the current managers are against its use for some reason.

Apparently the narrative film rights to his (major) speeches are owned by a single filmmaker/company.
I think I got this right but I'm not sure.

That's really too bad. Growing up where I did, I never really got much from simply hearing the speech in school. It's a bit of a read but here's an interesting article about my state's racist history, one that everybody likes to pretend didn't exist:

http://tinyurl.com/lacf6br

as such I didn't really understand the man by simply memorizing a speech and doing a report on him in 3rd grade the way I would through a film, or why, and this is totally true, people protested the renaming of a street from Union Avenue to Martin Luther King Jr. Blvd. In 1989.

good times

Dynomite!