Cameron, you wrote "My personal belief is that an NC license would be counter-productive (meaning the work couldn’t be used for teaching at a fee charging college or for research funded by a commercial sponsor for instance) ...". We have considered this at the DCC (which also currently uses a CC BY-NC-SA licence), and we think that under those conditions we would be perfectly happy to license the user separately, possibly after a negotiation of some kind. We realise that this means an extra, manual transaction, and it might not work well for data in terms of interoperability; it's the kind of thing worth reviewing after a while, but so far seems perfectly viable.

The cost in effort so far to us: nil. Lost use because of misunderstanding of the limitation? Unknown, I suppose!

I agree that the CC licences, with their backing legal text based in many different jurisdictions (eg a different text in Scotland than in England, because of differences in contract law), are much better than any vague forms of words such as the Matrix Cookbook authors used. For example, does their second sentence negate their first, if authors quoting their work publish in (say) an Elsevier journal, as Elsevier would be making money reselling an extract from the Matrix Cookbook? (Note, I'm not asserting this negation, just indicating their might be ambiguity).