I don't have a need for Dutch often, but it's a natural place for a start, obviously.
I don't know openNMT at all, but I'm willing to donate cpu cycles both at home and on my vps's (to the extent that they allow me). Maybe it works something like BOINC https://csgrid.org/csg/instructions.php ?
It's ambitious, but a previously solved problem several times over. That takes care of crunching the models. Dunno about actually using them in a responsive way on demand.
Thank you for your initiative.