If the answer is “until I don’t want to do it anymore” that is perfectly fine but then can there be a commitment to open sourcing (if it isn’t already) when you make that decision?
As an individual developer is the owner of the app and code I just want to know if the app will still exist in a year and be functional, otherwise I am not interested regardless of me liking the app idea.
If OP would like to charge money or accept donations or whatever they would like to do that is fine, but right now those questions are unanswered.
"Assume good faith" and that. Fair to ask, but show the courtesy due an equal at least until it is evident that is unwarranted. This engineer has done work demonstrating they are at least my equal and I am not prepared to treat them otherwise only because I have not seen them do so before. The 32/64 bit and Intel/Arm transitions should be enough warning for anyone and lie well within living memory.
Someone may cavil over "polish," I suppose. I have a 5-quart 'Artisan' Kitchen-Aid stand mixer in lavender, because that nicely sets off my kitchen decor and because I impose light enough duty on that machine to make aesthetics a reasonable figure of merit. This app is not that kind of machine. Who cares what color the cover plates are, when the target audience will never run the machine with them installed anyway?
(And unless there exists a design patent, why worry about a case where, at worst, you already know what market you need your product to fit?)
It’s not unfair to want to know whether the author plans to make it viable long term or if it is a project that is scratching their personal itch.
If it’s a project that’s only meant to scratch a personal itch and they only plan to support it for as long as they deem it useful and have no intention of open sourcing it in the future that is fine, I personally, and I’m sure other , don’t want to bother with it, that doesn’t mean nobody does but it answers a question and prevents disappointment down the line.
If the author has intentions of supporting it long term then asking about funding or long term development effort assists the author to think about something they might bot have thought about, or at the very least has the author clarify.
I’m fine with paying for polish, many users are.
Here the product is already made and in distribution, asking these questions isn’t preventing the project for getting going, they are the next logical step in the life of a project, arguably some of them should have been asked before “going live” like if you would like to monitise the project.
I asked a question in response to them asking me to download and use their app. Have we reached a point in this world where simply asking a question is offensive? They had every right to choose not to respond just like I can choose not to use their app if they don’t. How you respond is your choice, if you chose to take offence to a question about the long term sustainability of a project that’s on you, for me I don’t want to use software that has no intention of existing long term. If we have different values that’s fine, I don’t care.