It is in connection with the future policy, after the rtm. I would imagine it will apply to the  information you have registered on the insider program, not a specific computer.
If you only have a single such, then it will, naturally, apply to all your computers.
You have probably read the update, but, for other readers. Beware.  MS have moved the goal posts.
If you opt out of the insider program, after receiving your upgrade, it will, in time, become deactivated. The only way forward, then, is to purchase a licence.
Best path is to allow the offered upgrade to your Windows 7/8 machine through the normal channels.
After many months of battling with the builds, offering, and receiving advice, at this point I can see no real advantage...