Medical device manufacturers may be reluctant to use COTS (commercial-off-the-shelf) because it implies SOUP (software of uncertain provenance), and thus may compromise device safety and pre-market approval by regulatory agencies. If we make the distinction between opaque SOUP and clear SOUP, that is, SOUP for which source code, fault histories and long in-use histories are available, we will find that COTS software may be the optimal choice for many safety-related medical devices.