VMware Player isn't open source. Pixops is used by VMware player and so under the terms of the Pixops licence the code has to be made available for it, hence the download on the VMware site.
You can also find some open source downloads for ESX server. This doesn't help you out very much, because the actual virtualization software isn't available, but some of the Linux components that they use in the management console on ESX are available.
