I've been told that 10 will only be free for a year; after that you will have to pay a monthly fee.
The option to upgrade to Windows 10 will be free for 1 yr and then you will have to pay for the licence in full. In other words please upgrade and be our global testers.
Monthly may be a misunderstanding to the apps that may come with windows 10 as its going to be like your phone with a apps store.
Microsoft office 365 is a monthly fee for example.
