The Amazon Android/FireOS app-store is having a Halloween Free Apps promotion. A total of 29 premium apps are participating, and you can get as many of them as you want for free, including photography-app PhotoLab Pro by Vicman LLC. Other famous apps included are AVG AntiVirus Pro, Splashtop Remote Desktop, and lots of games.
These are Amazon’s regular apps, not the “Underground apps” that are free but your data usage is the price you pay for the free-ness. Offer ends 10/31/15.