The official ISO download link for Windows Server 2016 ISO (final release) is:
Welcome to BackupChain, the Server Backup Software for IT Professionals!
While you are waiting for your download, check out BackupChain, our Server 2016 backup software that is specifically made for IT pros. Among the many unique features you also benefit from a “lock-in”-free backup strategy that relies on open standard file formats. Virtual machines disk and database file sizes are reduced using deduplication and whether you backup to the cloud, Hyper-V virtual machine backup, VMware server backup, Exchange server backup, and complete file server backup. In addition to Windows Server backup, BackupChain also includes the tools you need to set up a DIY cloud server yourself on all versions of Windows from XP to Windows 10, to Windows Server 2016.