Quoting from the VMware official announcement:
VMware, Inc., the virtualization leader, today at VMworld 2007 announced that it has released a majority of VMware Tools as open source software as part of the project Open Virtual Machine Tools. VMware Tools is a set of guest operating system virtualization components that enhance performance and improve management of VMware virtual machines.
VMware is also working with operating system vendors including Novell, Red Hat and Ubuntu to integrate open-sourced VMware Tools into the operating system installation process…
Open source version of VMware Tools is available here.
With this move VMware hopes to spread VMware Tools adoption among all Linux providers, which may ship VMware-ready distros in a near future. At the same time VMware is trying to simplify huge work of supporting VMware Tools for a ever-growing amount of distributions which are updated at a very fast pace.
Anyway the move implies some risks: proliferation of non-official VMware Tools versions will increase chances of guest operating system instability and insecurity.
Steve Herrod, Vice President of Technology Development at VMware, told virtualization.info that the company will only support official VMware Tools, so customers should pay much attention to which version they are going to install in production environments.