Not really dedicated to open source course material, nor to free courses...
The "Open" in its name only made sense in the 60's, when it was founded, nowadays, there isn't much about this institution that is very different compared to traditional Oxbridge. "Cheap more online university" would be a more adequate name for it.
A system that would truly live up to the name "Open" in the year 2020 is the one described at the ideal university by Ciro Santilli.
Wikipedia even says that the initial focus was on broadcasting learning material on television and radio, so what happened to that now that we have an even more powerful on-demand tool called Internet!
They even created their own MOOC website, FutureLearn. But www.freecodecamp.org/news/massive-open-online-courses-started-out-completely-free-but-where-are-they-now-1dd1020f59/ mentions:
The course content is still free to access, but it’s only available for the duration of the course, and for two weeks after it ends.OMG. God why.
A few open sources at: www.open.edu/openlearn/free-courses. The 5-hour course on particle physics says it all.
www.youtube.com/watch?v=Pj0rbafFBak What's an Open University Degree Like? by Luke Cutforth (2021) mentions that it is more autodidactic/online, and it encourages part time learning.
youtu.be/rsWwffX-u0A?t=99 Open University - How does it work? by Matt Greg Vlogs (2017) shows that they do have their own custom institutional material. And it is not open???? Please. youtu.be/rsWwffX-u0A?t=222 mentions that there is no entry exam, and you can change your courses at any time, that is good at least.
Israel apparently also created their own version in the 70's inspired by the British one: Open University of Israel. Same story it seems.