| The big question about an implied patent license would be whether or not it is revocable. In the specific cases of the BSD and MIT copyright licenses note that the licenses do not say that they are irrevocable. A license granted for no consideration is generally revocable unless it specifically says that it is not. There are substitutes for consideration. It is an open question as far as I know whether or not those apply in the case of free software and make licenses like MIT and BSD irrevocable. If you use BSD or MIT licensed patented software that does not come with an explicit patent grant, you'll have to deal with these arguments if the patent owner decides to go to court: 1. There is no implied patent license, 2. If there is an implied patent license it is revocable and they revoked yours, 3. The copyright license is revocable, they revoked yours, and that implicitly revokes the implied patent license (even if it is irrevocable normally). It's so much safer to try to stick to licenses that say they are irrevocable and include an explicit patent grant. |
Sadly, although Facebook includes an explicit patent grant, it does not claim to be irrevocable. They even list one specific case where it can be revoked.