This one is going to sound grumpy.
I will revisit this topic again, since it has come up.
The EBay auction that Lancie1 referenced is illegal.
Nothing on the auction description describes it as "legal", only that the seller will "guarrantee[sic] software will load and run". In fact, the seller admits at the very bottom of the form that "Registration is not transferable(copied)".
RSI has recently cracked down on this sort of thing on EBay, asserting their "Verified Rights Owner" status and getting EBay to delete these auctions of pirated software. Evidently that fellow has sneaked under the radar, mostly because he is selling via the UK, I think.
As far as PLCCenter goes, I am skeptical of their software sales, too. They claim to sell NEW A-B hardware as well, which is NOT true. They are not a distributor and cannot purchase new A-B hardware from Rockwell.
The best answer for the original querent Blulus is that he can transport an activation key from work to home in order to spend his own time learning the software. There's nothing wrong with that.
Like it or not, RSI deserves the same copyright respect as anyone else.