Contrary to that old yarn about there being no such thing as a free lunch, gratis grub will be on offer at Reading Terminal Market today. More than 30 of the market’s merchants are participating in the giveaway. All you have to do is, download LevelUp, a Philly-based smartphone app that allows you to pay your tab from your phone, and purchase your lunch with it. LevelUp in turn will pony up as much as $10 toward your meal. The offer’s good from 11 a.m to 4 p.m.