free is never free and it has nothing to do with Oracle. If it comes to you at no cost from a commercial company, generally but not always, you are the product for sale.
OTOH, and for your consideration, both Solaris and VirtualBox are free (for noncommercial use) products from Oracle.
OTOH, and for your consideration, both Solaris and VirtualBox are free (for noncommercial use) products from Oracle.