VirtualBox is GPL2. If you install Oracles proprietary crap, that's your problem.
"This is called "dual licensing". Since Oracle holds all the copyrights to the VirtualBox code, or is at least permitted to relicense code that is owned by external contributors or other parties, we are free to choose the terms under which we license the code to our customers, or the open-source community. "
So any code you submit, you also assign to Oracle so they can release it closed source. So not totally open.