You can accept cash donations from geni. You cannot
have a guarantor
member called "geni".
True, if we want to give some form of membership to people that want
to completely hide their real names we would need a less official type
of member. However, while guarantor members real names do need to be
made available to the public on request, there is no need to link
those names to pseudonyms - pseudonyms can be kept private. Someone
could go through the list of names and try and work out by a process
of elimination who you are, but I think they would struggle, at least
once the list of members gets reasonably large. Also, we don't have to
give membership to every donor, people can just donate money and then
that's the end of our relationship with them.
If we are going to have a less official form of member I suggest not
using the word "member" to avoid confusion, "friend" is better.