Unix Wars, Redux
But licensing issues cannot be ignored. For every CPU that Linux supports, Unix or another clone is available. What Linux provides that Unix does not is a unified feature set across all the supported machines. The fact that Linux is licensed under the GPL means that a feature written on one architecture is available to the others, unless it is really by nature architecture-specific—and very few features are.
This feature-sharing among architectures helps give Linux the potential to outstrip Unix development in the long run. It certainly makes Unix vendors sweat, and with good reason. Linux has the long-term potential to cause Unix vendors to cooperate more fully with each other; if they refuse, Linux has the potential to eat away at a large part of their current markets.