I don’t know how long ATO have been in existence, they were not in my awareness until the last year or so. I’m not sure of their funding model, but there may be some ad funding or direct funding support from the tech industry? The site isn’t
As for the business model and applicability to FCI - while a B Corp would possibly have been suitable I think the idea of the FCI being a for-profit would not have been seen as appropriate for many.
My advice for the FCI would have been to set up a Community Interest Company (CIC) - essentially it’s a Company Limited by Guarantee (CLG) with a special section in the constituting documents that defines a ‘community’ it serves and each year you are supposed to consider how you have served that community. I have run two of these over the years (openGPSoC and Leigh Hackspace) and the organisational overhead and cost is really quite minimal - far, far lower than a Charity which seems to me a bikeshedding vehicle for committee-driven thinking and paralysis by groupthink and risk aversion.