It is perfectly possible not to cater to every feature request, without being rude. A single sentence like this: I don't have the time, energy, desire, nor

It is perfectly possible not to cater to every feature request, without being rude. A single sentence like this: I don't have the time, energy, desire, nor language knowledge to implement this feature. conveys completely the same information as Kovid's comments, with the benefit of not being aggressive and demeaning.