I'm Czech, and a long time user of Mapy.cz / Mapy.com. Monetization of Mapy.com has been a question for some time. It's part of the Seznam conglomerate, which makes most of its money through various news sites (including a TV channel) and an ad platform. Other "side projects" of Seznam, like their e-mail service, serve as drivers for their homepage and stay completely free. Mapy.cz contained affiliate Booking.com links for some time, but recently they added a paid subscription and moved the ability to download offline maps for more than two countries at a time behind a paywall. It seems that they are just now trying to figure out a more sustainable way to monetize, and everyone is hoping they won't destroy the great app in the process.