Microsoft License Windows 2012 R2

Can I update Windows server 2012 standard to Windows server 2012 standardR2 without a license update?

Standard and R2 require two different keys, so if you want to upgrade to R2 you will have to get a new key.

Windows Server 2012 and Windows Server 2012 R2 are two distinct products.

Thus, each require a separate product key to be activated.

If you have a valid product key for Windows Server 2012 R2, you should be able to upgrade your server.

Here are more informations regarding upgrade path for Windows Server 2012 R2 : http://technet.microsoft.com/en-us/library/dn303416.aspx

Hope this helps !