Non-dedicated computer clusters promise more efficient resource utilization than conventional dedicated clusters. Existing non-dedicated clustering solutions either expect trust among participating users, or they do not take into account a possibility of running multiple independent clusters on a same set of computers.In this paper, we argue how an ability to run multiple independent clusters without requiring trust among participating users can be capitalized to increase user experience and thus attract more users to participate in the cluster. A generic extension of non-dedicated clusters that satisfies these requirements is defined and a feasibility of one particular extension is demonstrated on our implementation.