VirtualBox is only partially open source and free: For example, USB2.0 and RDP support is non-free. https://www.virtualbox.org/wiki/Licensing_FAQ https://www.

VirtualBox is only partially open source and free: For example, USB2.0 and RDP support is non-free. https://www.virtualbox.org/wiki/Licensing_FAQ https://www.virtualbox.org/wiki/Licensing_FAQ Also note that they do openly admit that stopping to release under GPL 2.0 is not planned, but possible and they reserve the right to do so in future.