The plan is to offer a subscription service even if there's an offline component. For a bunch of reasons, it's the best approach for a one-person venture trying to get off the ground.
I've been an OSS user and supporter for a long time. I don't think I'll be open sourcing the core system anytime soon, but I'm very likely to release any useful NLP or ML-related libraries that are created as part of this project. Not sure what those will be or when they'll be ready, but I do have a mind to give back to the OSS community.
I understand. Fwiw I recently had a look at "cyberduck" again - they do a gpl+free(nag) binary+sale through windows/Apple appstore:
Not sure what kind of income they see, though.
I always prefer a Free software/open source solution - but I'm not sure how you'd monetize that. Maybe charge for the app (ios/android) - and provide a free/open self-host server solution, along with a subscription service and a web client? (The payment for the app would also grant access to the subscription, and for those that didn't want to self-host/wanted to support the project could pay for the subscription and use the web SaaS solution?).