Comment (by Roland Haas):

Both GitHub and Bitbucket have options to let the wiki be editable by anyone with an account which may increase contributions by non-maintainers who typically do not have accounts on the ET mediawiki wiki and for whom getting an account may be a barrier (it requires email to maintainers@einsteintoolkit.org and that one waits until @Steven R. Brandt or @Roland Haas create the account for them).

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2256/transfer-et-wiki-from-mediawiki-to