Most British universities are registered as charities

No, they are basically not-for-profits, or more precisely in british legal terms, "charities". By taking government funding (directly or indirectly through subsiding enrolment fees?), they have to follow some government rules, and all major ones do it seems: academia.stackexchange.com/questions/49187/in-what-sense-are-uk-universities-public/49188

A similar confusing naming pattern appears to apply to Public school.

In the University of Cambridge for example, all MA degree holders or higher appear to have some voting power: www.cam.ac.uk/about-the-university/how-the-university-and-colleges-work/governance (archive)

This adds an extra layer of difficulty for the average taxpayer to make changes to university policy, e.g. making universities publish all material with Creative Commons licenses. At most, voters could require this indirectly through the government funding requisites. It is a mess.

Not even the Open University seems to be very open!

Ciro Santilli once attended a round table in the early 2020s where a University of Oxford official from the IP licensing department. The University of Oxford took a 20% equity on spin-off companies, not an uncommon University IP ownership policy at the time. At one point, the officer clearly justified this along the following very official sounding lines (paraphrased):While noble sounding, this immediately reminded Ciro of Instrumental convergence, in the field of AGI philosophy. Or in other words, of course the best approach to maximize education and research outcomes of society is to first take over the world, and then implement those goals from there! See also Why Not Just: Think of AGI Like a Corporation? by Robert Miles (2018)

Notably, the University of Oxford was extremely protective of its learning material at that time, which was highly paywalled behind university logins, presumably with the rationale of having unique learning materials to enroll more paying undergrads. How can giving out free information to all not be the optimal way to "promoting education and research" is very hard to envision.

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