The landlord providing the tenant with shelter (and the labor of maintaining that shelter, fronting the capital for the ownership of the shelter, insuring the shelter, assuming the risks associated with ownership, etc) is in fact a "reciprocal contribution of productivity". He is engaged in collecting rents, but he is not rent-seeking, which is the process of capturing value without providing anything of economic value in return. The exchange of money between landlord and tenant results in a net economic gain for both parties, and is therefore not rent-seeking, while the tenant exploiting government restrictions on evictions to capture shelter without providing a reciprocal contribution is engaged in rent-seeking (specifically, he is seeking the landlord's rents!)

If you read past the first sentence of the article it explains this quite clearly.