The tab is not new and Open Source downloads have been available for many years, you probably just hadn't notice it before now! Image may be NSFW.
Clik here to view.
As an example, the VMware-ws902-open-source.tgz
file is not a Open Source installer like the normal installer VMware-workstation-full-9.0.2-1031769.exe
file is and is instead a collection of Open Source programs that VMware may in some manner utilize in is proprietary finished product.