This is really the primary value proposition of Free and Open Source Software. No matter what happens down the road, no one can suddenly jack up licensing fees. Even if one company decides to try to change the direction of a project (Oracle; OpenOffice), another group can fork it to keep it going (LibreOffice).

Alternatives to VMware like KVM aren't just a better version of VMware that happens to be free, but it's fundamentally better because it is free (as in speech, of course).