For version 6.7, the "client" is built into the vCenter Server Appliance (vCSA). You don't download it separately; you access it via a web browser directed at your vCenter IP. ESXi Host Client:
Similarly, this is built into the ESXi 6.7 host and accessed via vmware vsphere client 6.7 download free
To download the VMware vSphere Client 6.7 (often referred to as the HTML5-based client or the legacy C# client depending on the specific version), you generally need an active Broadcom/VMware account with valid entitlements. For version 6
The official and safest way to acquire VMware software is through the Broadcom Support Portal vSphere Client (HTML5): For version 6.7