Budgies enjoy having 'freedom', out of their cage, however, they must be friends of yours or ideallt part of the family.
By this I mean for you to spend time with them so that they get to know you.
Initially give them a limited flight span and limited flight time, this ensures they will stay with you.
It can be very entertaining, I remember a friend of mine who owned a pet store, helet most of his loose and they would fly all around the shop. Now and again they would fly outside but with his carefull training they always came back. He even allowed some experienced birds fly around the shop at night.
I have since been in to his shop with 'new' owners. No flying birds, dull and dreary.