for EDU registeration you have to take approval from Domain country Government. Let suppose you want to register .com.au then you have to give letter to Government for asking Domain registeration.
It'll depend on each country's decision to allow sale of .edu.* domains. Most countries reserve this domain for educational institutes.
I've had a look, but I believe you have to contact whoever is in charge of the TLD to be approved. I also imagine it could be quite expensive, I may be wrong though.