We explore the creation of a metacomputer by the aggregation of independent sites. Joining a metacomputer is voluntary, and hence it has to be an endeavor that mutually benefits all parties involved. We identify proportionalshare allocation as a key component of such a mutual benefit. Proportional-share allocation is the basis for enforcing the agreement reached among the sites on how to use the metacomputer's resources. We introduce a resource manager that provides proportional-share allocation over a cluster of workstations, assuming applications to be master-slave. This manager is novel because it performs non-preemptive proportional scheduling of multiple processors. A prototype has been implemented and we report on preliminary results. Finally, we discuss how tickets (first-class entities that encapsulate allocation endowments) can be used in practice to enforce the metacomputer agreement, and also how they can ease the site selection to be performed by the application.