You can download as many copies of avast as you like the download doesn't install avast if you select save as or save file as so the file is saved to your hard disk (at your chosen location).
You don't have to give your email to download avast only when you register it (Home version) or if you buy the pro version. You don't say what version this relates to ?
I never delete my avast installation file but save it to my downloads, security-apps folder available to use if necessary.
You can use the same registration key for multiple copies of the Home version, provided that their use is for home, non-commercial use (both must apply) and obviously be in the same home.
