Windows licensing options

This article discusses all available Windows licensing options. It includes description of the features of open licensing, SPLA, CSP, VDA and RDS licensing.

Open licensing

The Open licensing scheme provides an one-off purchase of Windows Server licenses and the customer must buy the Software Assurance (SA) maintenance contract separately on additional cost. The SA is optional but if the customer changes their mind in the future and wish to buy SA at a later point in time, they are charged retrospectively for the amount of time passed since they initially bought the product.

Open licensing also requires the purchase of separate Windows Server CALs for each user which is going to be connecting to the server (per device or per user CALs). If the customer wishes to run RDS infrastructure, additional RDS CALs are required per user. RDS CALs are charged initially based on the total number of users purchased (regardless of the actual number of users logging in each month).

All licensing is based on server’s total physical cores. Minimum charge is for 16 pcores per physical server. Windows Server Datacenter edition allows for unlimited number of VMs. Windows Server Standard edition allows for maximum of two (2) VMs per licensed physical server. There is however limitation with regards to license mobility. This means for example that in a HyperV cluster scenario, each physical host can run a maximum of two (2) VMs. If there is a total of four (4) VMs in a two-node cluster, then each cluster must have maximum two VMs, i.e. no license mobility is allowed. In case of a disaster of one physical node, all VMs can be moved to the second physical node but must remain for minimum of 90 days and then be moved back to the original host. For each additional two (2) VMs to be supported per physical host, additional standard edition licenses are needed to cover twice the licensed pcores.

Open licensing Software Assurance (SA) offers a disaster recovery option which allows the usage of an extra physical host which can be offline and only be used in case of a disaster, without additional cost. Open License is a good choice if you prefer a pay-as-you-go model a have a minimum initial purchase of five software licenses. Software assurance is an optional purchase with Open License.

Open licensing alternatives in CSP licensing

As per, there have been various changes introduced to the Open Licensing program. Read through the previous article to be informed about all relate changes and about the successor Open Value and Open Value proposition programs. Also the CSP plan will introduce the option for perpetual software licenses under CSP. The Microsoft CSP licenses can be either subscription based or CSP perpetual. All CSP licenses are issued on your customer’s name and require that your customer has a Microsoft 365 tenant. All CSP licenses will be shown and managed via the M365 administration portal.

The Microsoft CSP perpetual licenses inherit all Open license characteristics mentioned in the previous section of this article but they do not include Software Assurance. If your customer needs software assurance, they can choose the Open Value or Open Value Proposition program. Another alternative which is especially useful and makes sense in hybrid installations with Azure Hybrid benefit is for the customer to choose the CSP subscription license for Windows Server. This type of license allows for Azure Hybrid Benefit, similarly to existing Open licenses with Software Assurance.

SPLA licensing

The SPLA licensing scheme provides recurring monthly subscription of Windows Server licenses (called Subscriber Access Licenses – SAL) and the customer does not need to buy the Software Assurance (SA) maintenance contract. SPLA provides access to latest product versions.

Microsoft also provides entitlement for disaster recovery components to be licensed without additional cost, as part of SPLA Windows Server licensing. Special terms and conditions apply. All licensing (SPLA SAL licenses) is based on server’s total physical cores. Minimum charge is for 8 pcores. Windows Server Datacenter edition allows for unlimited number of VMs. Windows Server Standard edition allows for maximum of one (1) VMs per physical host. For each additional one (1) VMs, additional standard edition licenses are needed to cover twice the licensed pcores. Again there is no license mobility, so in case of eg two VMs, only one VM can reside per physical host.

The above SPLA licenses (SPLA SAL) cover unlimited user access. If the customer wishes to run RDS infrastructure, additional RDS CALs are required per user. RDS CALs are charged initially based on the total number of users purchased (regardless of the actual number of users logging in each month).

Remember that the SPLA program assumes that you as the service provider have administrative access to the infrastructure where the SPLA-licensed products are deployed. You should not disclose the SPLA licensing keys with your customer, since these keys are issued to you (the service provider). The SPLA license keys are managed via the Microsoft Volume Licensing Service Center (VLSC).

Windows Server OS licenses vs Windows Server CALs vs RDS CALs

A Windows Server CAL is a license that allows customers to access Windows Server. CALs are used in conjunction with Microsoft Windows Server OS licenses (Open or SPLA) to allow Users and/or Devices to access and utilize the services of that server OS:

  • Per User CALs allow a single user access to Windows Server from an unlimited number of devices
  • Per Device CALs allow an unlimited number of users to access Windows Server from a single device

When it comes to RDS CALs, they are different than the server CALs stated above and are required for users or devices that want to utilize Remote Desktop Service (RDS) functionality on a Windows Server. RDS CALs can also be either Per Device or Per User. More details about RDS CALs can be found at: Also a deep dive on Microsoft RDS CALs can be found at:

Windows 10/11 supported licensing scenarios

Windows 10/11 can be used in a hosting environment in the following two supported scenarios:

  1. VDI. Making use of VDI in a hosting infrastructure requires Microsoft VDA licenses. It is officially supported only in enterprise environments, i.e. not generally supported under SPLA. SPLA still requires usage of only Windows Server based images (Server OS). The only exception to this rule is if a hoster is a “qualified multitenant hoster”. A qualified multitenant hoster is a hoster which is both SPLA and CSP partner and is Tier 1 partner. In the case of VDI scenario of Windows 10/11, it is important to define which licensing model is being applied (Volume licensing aka Open Value, CSP or Enterprise Agreement). The Microsoft VDA license comes in two flavors, similarly to the server-based RDS license, i.e. as per-device and per-user VDA licenses. In the case of Open Value, the MIcrosoft VDA license are by design pre-device licenses. In the case of CSP licenses, there is option for per-user licenses. Bear in mind that the Microsoft VDA license must be applied at the server-side Windows 10/11 VM level but it is accounted for each remote user or device connecting to the Windows 10/11 virtual machines which are used as virtual desktops. Also it is important to know if a customer has an active Microsoft SA agreement in place. If so, a Windows Enterprise license with active SA accounts also for VDA licensing rights, without the need for purchasing an extra VDA license. The full documentation with all license terms and licensing options for Windows 10/11 VDI scenario is available in the following article:
  2. Local virtualization. Client machines running Windows 10 with Hyper-V in order to host a virtual machine for testing / development purposes.

All other usage scenarios with Windows 10 in a hosting environment are generally unknown as per MS documentation (grey area) and are not supported.

For all other usages, an alternative Windows 10 license (DSP, OEM, Retail) license is required.  It must be noted that retail licenses cannot be used in BYOL (License Mobility) cases.

Windows 10 Enterprise Multi-session and Windows Virtual Desktop (WVD)

CSPs are currently waiting on potential upcoming licensing changes for Windows 10 clients which are configured as multi-session clients. Windows 10 Enterprise multi-session, formerly known as Windows 10 Enterprise for Virtual Desktops (EVD), is a new Remote Desktop Session Host that allows multiple concurrent interactive sessions. Previously, only Windows Server could do this. This capability gives users a familiar Windows 10 experience while IT can benefit from the cost advantages of multi-session and use existing per-user Windows licensing instead of RDS Client Access Licenses (CALs). For more information about licenses and pricing, see Windows Virtual Desktop pricing. In its current state, Windows 10 Enterprise multi-session cannot run in on-premises production environments because it’s optimized for the Windows Virtual Desktop service for Azure. More details about this can be found in the following article:

License mobility (Bring Your Own License BYOL)

If the customer has SPLA or Software Assurance in Open licensing, they can bring their own Microsoft licenses to a hosted environment (CSP infrastructure) and use them in parallel with the CSP’s SPLA licensing. Special terms and conditions apply. The supported BYOL scenarios are described in the Microsoft SPLA Overview.pdf document. In order to enable BYOL options, both the hoster and the customer must fill-in a form and submit it to Microsoft. The hoster only carries this out once and each customer must submit a separate form each time they need to make use of BYOL. The following documents must be signed and sent to Microsoft:

  1. License Mobility Verification form – This is the customer form which designates all products which are applicable for license mobility (active SA is required). Office is not included. Office does not include license mobility.
  2. SPLA License Mobility Addendum – This document assigns the mobility partner title to an existing CSP partner.