Just been reading here and I have a much better feel for the problem now, or so I thought, but I had still to find the solution.
My members need to be on one domain/site, and the public needs to be on the other. Only problem is, both sites need their access levels protecting and I want to have an SSO (single sign on).
Anyway, then I found this WordPress 3.0: Multisite Domain Mapping Tutorial which tells me
This will make your login pages for all sites redirect to your main site to do the actual login. The benefit of this is that when you log in to one, you log into all of them. The downside is that the URL changes to another domain in order to log in.
But the downside are not downsides for me and the upsides are what I want.
And then again I found this at WPMU.DEV…
However, and this is the reason I use Doncha\’s plugin, the WPMU DEV plugin does not handle remote logins. On a multisite network where you want folks to be able to browse the network, and still be logged in to all sites regardless of domain, only Doncha\’s plugin handles that (it also handles ajax along with this – the WPMU DEV plugin does not).
And then, later on, I find this…
Domain Mapping plugin – Lets all sites within one network have a domain mapped. This does not support single sign on. Multi Domains – This allows a WordPress install to run multiple networks. Each domain is owned by you and has single sign on.
So now I am really confused…
P.S. I wonder, can I just request it as an additional function to s2Member if I buy PRO?… 8^)