Reading over the actual website (happipad.org), on the face of it, it looks like something voluntary.  If it's nothing more than connecting homeowners with lodging-seekers, whether through some sort of rental arrangement, a trade of housing for assistance with one's needs (e.g., an elderly person who needs assistance with some non-medical tasks), or a hybrid of both, it's hard to find fault with it --- as long as the homeowner (and, conceivably, the home-seeker) has veto power over whether they accept the other party or not.  "Taking in boarders" has always been a "thing", as has unrelated people joining their efforts as roommates --- in the DC area it's practically a way of life.  Very often, in the DC "roommate culture", you will have successions of renters, Adam and Barney get an apartment together (and, no, they're not necessarily ɧoɱosɛҳųαƖs), Adam moves out, Barney has Cecil to move in, Cecil moves out, Dan moves in, Barney moves out... you get the idea.  As long as the landlord can keep the apartment rented, and the roommates pay their rent on time, the landlord shouldn't care.

Again, as long as it's voluntary, and nobody is forced to accept anyone as a roommate, no problem.  But if you start having "diversity" forced upon you, or are even forced to take in someone you don't want to take in, then that is a problem.

I actually like the no smoking rules.