This document discusses the sustainability of scientific software in complex ecosystems. It notes that while the ability to recombine digital information is beneficial for innovation, it also threatens sustainability by increasing the work needed to maintain software as usage diversifies. Three models for attracting resources to do this work - commercial markets, open source peer production, and grant funding - are examined. Grant funding is found to be weakest at gaining visibility into diverse usage contexts. Improving sustainability therefore requires either suppressing recombination or incentivizing greater visibility into how software is recombined in practice.