They seem to not ask any trades from the users. No ads injected into their website, no data collection for making a profit off of it, or asking any currencies in return for this website’s service. I never used this service but that’s from what i could dig about them. Here’s what Wikipedia says about them:

"BeWelcome minangka layanan jejaring sosial sing bisa diakses liwat situs web sing digunakake kanggo ngatur homestay lan perhotelan. Platform kasebut minangka ekonomi hadiah; host ora diidini ngisi biaya penginapan.

BeWelcome dilakokno dening BeVolunteer, organisasi nirlaba sing diatur minangka asosiasi sukarela sing didaftar ing Rennes, Brittany, Prancis, sing mung dumadi saka sukarelawan. Piranti lunak ing mburi situs web, platform BW-rox, yaiku piranti lunak gratis lan mbukak-sumber.

https://en.wikipedia.org/wiki/BeWelcome