FRANCESCO GUARASCIO LEADERS of the world's largest economies back "voluntary licensing" of COVID-19 vaccine patents, the draft conclusions of a summit show, watering down a U.S. push for waivers and earlier commitments to supply more funds to the World Health Organization. The draft document, seen by Reuters, lists commitments of G20 nations and other countries and is to be adopted on Friday at a Global Health Summit in Rome, one of this year's major events to coordinate global actions against the pandemic. The draft, which is still subject to changes, is the result of a compromise among experts from G20…