I think this is really missing the point of the question. I know that it is common for endowments to be invested "in the market" - people believe that's the most responsible thing to do. But the question was about why do things the normal way? Why link up market performance of a set of investments with funding mechanisms for OSS? If you're going to be bold and try to fund something that is, in market and economic terms, quite off-norm, why do that using entirely normal systems that are at the core of a capitalist economy?