has been and is

The first example uses the perfect tense. It has a focus on the fact that the activity is currently in the completed state based on something that happened in the past.

You would use the first example if you are enquiring about whether somebody has completed the activity, and as a result it is now complete.

The second example uses a simple copula. It focuses on the current state of the activity being completed, but does not infer that a past event made it this way.

You would use the second example if you are enquiring about whether the activity is currently in a completed state - but not interested in whether it transitioned from being not complete to being completed, or whether it was always in a completed state.