i work with maintenance of PCs, i use avast! home in my customer’s PCs. i want know if i can use the same serial at all customer’s computers. i’m waiting some answer. good bye 
No.
They can initially use the Trial Key that gives 60 days unrestricted use but the would require their own registration key. They after all are effectively responsible for afirming that they are using it for non-commercial use. It is also better for them to register because they will be sent their own registration key whivh will be valid for 14 months avast! 4 Home Registration.
This is how Alwil know how many active users there are so they can manage server load/support for the VPS and program updates.