It is a criminal offence under s9 of the Bail Act 1976 to agree to indemnify a bail surety. If Assange's guarantors had entered into an agreement with Assange, that agreement would have been illegal under English criminal law, and thus an unenforceable contract.
This goes a little off-topic, but you might be pleasantly surprised about Crown Copyright.
Crown Copyright doesn't deal with university research, only with works done by the government. Pretty much everything released by central government is now licensed through the UK Government Licensing Framework under the Open Government License (OGL), which is essentially CC-BY.