Yes, you'll be typing Nu code in a Nu interpreter.

Even though it's a Lisp dialect, Nu was designed from the beginning to be interoperable with Objective-C, so translating between them is easy. (Convert brackets to parentheses and you're 80% of the way there.)

As a contrived example, this:

  if(![self.address startsWith:@"https://"])
    self.address = [@"https://" stringByAppendingString:self.address]

Becomes this:

  (if (not (@address startsWith:"https://"))
    (set @address ("https://" stringByAppendingString:@address)))