[octref]

I have thought about building a vocabulary learning tool for learning Japanese on top of Apple Dictionary. My idea is simple: user collects dicitionary items and the tool offers lookup / spaced-repetition.

However, I'm concerned that the dictionary is copyrighted. Is there any precedent that says whether such a tool would be legal/illegal?

[tasogare]

If your tool doesn't come with bundled data from Apple, extract data in local and doesn't leak it to another party it's probably safe to do so (like emulators).