I use this word every time an "employee" leaves my office. I surely am not firing this person...
> Sir, nothing at your orders ? < No sergeant, you are dismissed.
In international military environment it's used as a term to indicate that orders are executed, the superior is satisfied and the person who was under kind of contract (executing an order, a work a mission) can continue other works that were not ordered or agreed upon.
In this context : milestones achieved, thank you for colla and moving on with business...