You sound quite inspiring. Better to go with ambitions for growth than wither on the vine.
Being sceptical the highlighted is an issue for many not for profits; they become self serving as they become older. They have real people with real lives who have to earn real money to staff them. Their prime objective re JREF should be education with the funding secondary to allow this. I was involved with a small charity, the charity had ambitions to grow, the professional fund raisers brought in cost more than they raised, the charity folded.
Many charities would have leveraged the equivalent of the forum. E.g. ask you to sign up to get emails from them, fund raise etc. I guess from what you say the Foundation board decided either the cost of hosting the Forum was more than the potential benefits to the Foundation, or as seems to be hinted at the risks of litigation and consequent costs are a risk that the Foundation could not bare. The latter seems a better explanation than the former, one aggressive litigant could easily screw the finances of a small organisation; if they have legal insurance then I can easily see the insurers saying that dumping the forum will reduce your potential liabilities and make the insurance cheaper.
FWIW I would sign up to transfer to the new forum. I am not convinced that the US is the best place to host the server but understand the bulk of membership resides there.
Of course the JREF was created in order to educate. However, the organization's plans to educate cannot be accomplished without funding. Therefore, funding is of the utmost importance, because it allows the JREF to educate. That's a chicken-egg argument. It doesn't actually indicate the JREF is "self-serving".
As to the rest, you are forgetting one major thing - the forum is labeled 'JREF' which means the content needs to comply with the JREF's brand (and the JREF *is* a brand). While having a forum liaison to set rules handed down by the JREF allows them to exert some kind of control, rules can't be set for things like tone, style, and content beyond general guidelines like "no smut" and "no cursing". When a believer comes in here, sure, there are some fantastic posters who present well-reasoned arguments and treat the newcomer with respect. There are also a high number who only stop in to snark, bully, etc. That isn't a great branding strategy for an organization concerned with outreach.
The JREF has to be concerned with public perception. Do we put a good face on the JREF? We couldn't even stop ourselves from sniping at a JREF staff member whose intention was to help.
Now, if we were the majority of the JREF - if we all had memberships, and we were all donors - maybe that wouldn't matter. It would certainly offset the damage that we can do. But we don't offer that value. So, explain to me, why would the JREF want to keep the forum?
And again - I wish the JREF had massaged the forum into a better place. It's kind of a free-for-all in here. Lots of snark, lots of infighting, people skirting the rules so that they can still get away with calling other posters stupid like somehow that's a meaningful contribution.
Maybe if we had celebrity AMAs we would put on a better face, or if we had a goal for the forum as a whole we would be united. But let's keep in mind here that the mods had to start up a rule disallowing threads on GUN CONTROL, of all things, because users were starting them only to continue infighting.
And what I'm trying to say is - this is our chance to be united. This is our chance to have opinions and be heard and lead this somewhere other than an internet fight between a tiny population of people over things that are essentially meaningless because we never actually DO anything about them.