Hi,
It means that melonJS is able to display isometric map, see this example:
but does not contains yet built-in code to manage collision (as opposed to orthogonal maps).
actually i'm working on it now, I more or less just added the necessary code to render properly isometric map, with my next step being to look at isometric collision detection.
I can't however promise you for when this will be ready, so unless you are ready to dive into the code and help on this, you will have to wait a little bit :)
and about how to add collision management (in a proper way), that's an answer I'm trying to find as well.
I know that AndyV3liz was working on an isometric game, so he might have some answer to provide )