Unless they've gone around and bought up the rights to these titles, their names and IP, then this cannot be legal.
Just because a game was released on the Amiga doesn't make it the property of Commodore or of any company that subsequently bought the name or various rights to the "Amiga" ... whatever that means given all of the possible rights and licences involved.
It would be like releasing a game on Android and then Google owning the IP!
Many companies will have just folded and disappeared, some rights owners will have passed away thus making tracing who really owns things quite tricky in some cases. Mostly though old games companies get their IP purchased when they go under. Look at THQ and the sale of it's "assets". So in many cases these IPs are going to be owned by much larger corporations, they just might not have realised it yet.
