You can distribute material by uploading files to this forum. There are clear limitations of course. And Creative Commons CC‑BY‑4.0 licensing is mandatory. There is an openmod GitHub account, see here. But I don’t have other details.
Regarding an etherpad‑like service. It would be possible to create a private topic on this forum limited to workshop participants and then make the top posting a “wiki posting” editable by anyone with access. Again clear limitations there too.
On the upside, use of the forum keeps the material together.
Regarding GitHub, the log‑in process is rigorous these days with two‑factor authentication and special apps and/or hardware required (no doubt driven by United States government concerns about software exports to hostile regimes). For instance, I can only log‑in from my laptop, which I will leave at home. HTH, R