According to Microsoft's licensing policy, a separate license is required for each server that is running Windows Server software. Therefore, if the DR server is running Windows Server software, it must be separately licensed.
However, if the DR server is in a passive mode and not actively running any software, then it does not require a separate license.
It is important to note that the licensing requirements may vary depending on the specific licensing agreement and terms of use.
It is recommended to consult with Volume Licensing Support Info. | Microsoft Learn for further guidance on licensing requirements.