[Deestan]

> In Norway, it's usual for employees to sign intellectual copyright waivers for all work done for their employers.

Yes, but that does not seem to be what this is about. On the surface it seems he was re-using good ideas rather than copying over actual work.

The nettby case was about outright copying source code.

[Androidmeda]

Re-using ideas/features he was paid for at Opera? Doesn't that make those Opera's property?

[eliasmacpherson]

Only if the contract signed says so. There's usually a standard section in the contract for this sort of thing so it really depends on that.