In a nushell, this will be free for business users. Professional vs Enterprise users its a different path to get there…
Larger customers that have valid Software Assurance contracts in place, running Windows 7 Enterprise or Windows 8 Enterprise, essentially are licensed for the free upgrade anyway.
Any Pro version of Windows 7 and Windows 8 (which most small and medium-sized businesses use) will get the upgrade to Windows 10 for free over Windows Update, just like those designated to quote/unquote consumers. If a larger company allows their SA contract to expire, they only need to downgrade (downgrade rights are included) to the Pro version of Windows and connect it to Windows Update to get the free upgrade.
What about my WSUS server and these ‘branches’?
“Microsoft is also going to offer “Current branch for Business,” which is aimed at customers who are willing to receive not just the regular security updates to Windows 10, but also feature updates “after their quality and application compatibility has been assessed in the consumer market.” Users on this branch will give IT departments time to validate updates before they deploy them to their employees. Customers using this branch will have the option to receive updates automatically, via Windows Update or via WSUS.”
Microsoft is expected to provide customers who take advantage of the free Windows 10 promotion with regular, free feature and security updates on an ongoing basis via Windows Update, most likely with little or no opportunity to decline or delay either.
What about compatibility? Easy – if your running 7 or 8/8.1 (which are upgradable) – your all set!
So, really. When you look at from this perspective, Windows 10 will be a free upgrade for everyone – either through Windows Update to Pro versions of Windows, or through an existing contract. If you want to get all technical, and exacto about it, yes, it does cost a little, but you’re really paying for the other, bundled services and products – not Windows 10. And, this speaks a little to what Microsoft has dubbed “Windows as a Service.”
Servicing Windows 10 is the piece that is still most unclear and the one area where businesses might find additional charges.
More details here-