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 ndi malo ochezera a pa Intaneti opezeka pawebusaiti yomwe imagwiritsidwa ntchito polinganiza anthu ogona kunyumba komanso kuchereza alendo.

BeWelcome imagwira ntchito ndi BeVolunteer, bungwe lopanda phindu lopangidwa mwaufulu lolembetsedwa ku Rennes, Brittany, France, lomwe limapangidwa ndi anthu ongodzipereka okha. Pulogalamu yomwe ili kumbuyo kwa tsambalo, nsanja ya BW-rox, ndi pulogalamu yaulere komanso yotseguka. ”

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