License key has been updated to the most recent version.
Current license key number is PLSK.0123456789.1234.
Plesk automatically renews its license key every three months, and by default the server is setup to notify the admin.
You'll only see this on a VPS or dedicated server, Windows or Linux.
It's expected and normal behavior.
While you can turn it off -- don't. If there's a renewal error due to whatever reason (network connectivity being most likely), then you won't get notice of failure. And then your panel may shut down after the grace period ends! That would be a situation of making a bad situation worse.
Need a good host?
Find one here: List of the Best Web Hosts in 2012 - Shared, reseller and VPS hosting