Thanks for your feedback Patrick. As you probably know, the Open Source Initiative maintain The Open Source Definition. When OSS Watch (and indeed the Cabinet Office) refer to "Open Source" we mean software which fits within that definition, i.e. is released under an OSI-approved licence.
I agree that the governance and development models of a piece of software are important to consider when procuring a piece of software, although they are beyond the scope of this document. OSS Watch also provide training and guidance around assessing these areas of a project to make sure it's suitable for your institution's goal. We have several tools for assessing the openness and sustainability of a project which are documented on our website and we're available to help people make use of these (not trying to make a sales pitch, I just want to be clear that we are aware of these issues and aren't presenting the document in isolation). In particular, we have a guidance document explaining how to best make use of "Open Source Options" type lists.