Depends on what you’re trying to change.
Editor has (and will be much improved upon in the next update) script-like capabilities via triggers.
The UI is a script itself.

But not for things like AI (except what is already exposed via parameters)

The idea was to release the entire source code, allowing for full modification. But that will probably happen after the game’s full release on Pc and mobile platforms.

Woah that would be absolutely nuts and lead to amazing community creations we cannot even think of yet. Seriously that would be heroic.