To rephrase again... regarding patents, assuming you don't first sue RedHat or Facebook, then:
RedHat won't sue you over your FOSS project that infringes any of RedHat patents, but your proprietary software is fair game.
Facebook won't sue you for infringement caused by using one of their libraries in your software (FOSS or not), but your independent project (FOSS or not) that infringes any Facebook patent is fair game.