I lived in CA until a couple years ago, here's my answer based on CA firearms law then, if you want up-to-date then ask at calguns.org.
There is no actual gun "registration" requirement in CA. In other words, merely because you own a gun, doesn't mean you have to "register" it. (Not applicable to unusual firearms like Class 3).
Any paperwork requirement comes when ownership of a gun changes. Then the transfer has to be done through an FFL.
AFAIK, even if it is a gift. In your friend's case - who legally owned the guns when the guy died, his heirs I assume? Would have to get one of the heirs (kids) to go down to the FFL and sign the transfer papers w/ your friend.
As a practical matter, if I was your friend, I would not go through those hoops. I'd simply keep and use the guns. Depends how paranoid he is.
Legion is mis-informed though well-meaning. The "drop test" in CA does not apply to transfers of used guns, only to what new handguns may be certified for sale in CA.