The Short Version
Google released Fitbit Air hardware blueprints publicly, including material safety rules requiring lead-free alloys and no latex allergens, letting any manufacturer build compatible bands.
Google published the full blueprints for Fitbit Air bands and accessories, meaning any manufacturer can now build compatible gear without asking permission. The specs include lead-free alloy and latex allergen requirements, so Google is setting the safety floor, not just opening the door. Apple controls every millimeter of Apple Watch band compatibility. Google just handed that control to the crowd.