That is correct. A multi-boot system can be thought of as 2 or more separate OSes sharing the same hardware. Applications that you wish to run on more than one of these OSes must be installed to each one that you want to run it on and, if the application requires activation (as is the case with Anti-Virus), it must be activated on each OS separately and with a unique key if necessary. For information, I am using Avast! on my system (4 OSes, 4 installs) and I can use the same activation key on each install. Other AVs may be different.