For some years, Princeton's "Einstein Papers Project" has been working their way though Einstein's published works and private papers, publishing them in printed volumes, and also making all the content available online for free.

Their website has been offering every published volume online for free since 2014.

It's been a great resource for anyone interested in learning more about Einstein.

AIP Press Release (2014):

https://www.aip.org/library/einstein-papers-now-online

It was at:

https://einsteinpapers.press.princeton.edu/

Einstein died in 1955, so under the usual "death plus 70 years" copyright rule, all his original works, by default, might have been expected to become copyright-free this or next year. Many of his earlier works were non-copyright anyway, due to his status as a German citizen, and to Germany losing a couple of World Wars (which resulted in German citizens and publishers losing intellectual property rights). The "German IP" issue is presumably why Einstein's "popular" book was published in the UK for years with the original copyright notice removed.

For the last few days, the site has been inexplicably offline. Now it redirects to

https://einsteinpapers.press.princeton.edu/einstein-database/

Apparently Princeton University have now struck a private deal with Paradigm Publishing Services, to remove all free access to this material so that it doesn't undercut the business model of a new paywalled website, to appear next year, and to be run by PPS.

This seems to be someone's opportunistic attempt to restrict and monetise a body of information that was supposed to be made freely available, and was just becoming free of residual copyright restrictions.

Apparently the new paywalled site will be available in 2026, and they've presumably taken the existing site offline without giving advance notice, to stop people scraping the content and making it available for free. I don't know if this is legal, but it seems to be a "done deal".

PPS aren't saying exactly when the new site will be online, or what it will cost. They suggest that institutions contact them to negotiate a price for their members. Presumably they'll be charging roughly what journals charge, which suggests quite a high price for each document retrieved, for members of the public.

"Request a custom quote or more information! To learn more or ensure access for your patrons, fill out this form to get started today."

The people I feel most sorry for are those who worked on this project for years, thinking that they were contributing to an altruistic project that aimed to expand humanity's freely available knowledge, without realising that Princeton would then go and sell the project out, selling online exclusivity to all the material to a company that could then make money by charging access via a paywall.