I believe the thinking is that if your business is still around after the 3 years of free licenses, it is successful enough to afford to pay for licenses from that point forward.
That's still about on par with wireless carrier definitions of "unlimited" -- not a good trend to set. Don't use the word free unless its truly cost-free.
Most importantly it is free for 3 years without any obligation to ever pay anything. It is clearly intended to convince you to choose to pay in the future, but it is still free.
