Until now KMS support for Windows 10 clients has only been available on Windows 8, 8.1, 2012 and 2012 R2.
But now Microsoft has released an update that enables Windows 7 and Windows server 2008 R2 KMS hosts to activate Windows 10.
https://support.microsoft.com/en-us/kb/3079821
http://larslohmann.blogspot.dk/2015/07/windows-10-kms-keys-and-kms-server.html