"Generally petitions are to someone, some authority or company, asking for some sort of change in their policy. What does a petition addressed to no one add to the rest of the initiatives?"
The idea behind this petition is to create a permanent record so that folk can show their commitment to the GCC and be held accountable over it. The folk who have signed the petition are willing to take concrete actions to help put an end to male-only (and-male-almost-only) conferences and volumes. By making their commitment public they can also inspire others to follow their example; this way people of good will know they are not alone in trying to improve the discipline.