Grammar: He is gone vs He has gone

Both are grammatically correct, but convey different meaning. 

He is gone shows the present state.

It means he is absent, away or dead. Or he has left the country, or service.

This is often used for a permanent, or long term or dramatic absence like death.

 In the sentence He  has gone the verb is in present perfect tense. It means he has departed recently and will be away for the time being. Here the action is completed. 

He is gone is more about the current status. He has gone is more about the action completed.