The way I interpret it is, explicit patent license implies _less_: - Explicit patent license specifies why / how it can be revoked. - Without an explicit pate

The way I interpret it is, explicit patent license implies _less_: - Explicit patent license specifies why / how it can be revoked. - Without an explicit patent license, patent infringement case (by Facebook) against a party that uses Facebook's OSS would be become harder, because one may argue that such grant is implied by Facebook open sourcing the software.