Software patents affect a small part of the world. As a citizen of a state, where software patents are not a thing, I am personally not concerned with that. However, as a developer I am concerned with my clients, as many of them are citizens in states, where software patents are a thing.
The question is about the liability of the end user - are end users potential targets for prosecution on basis of software patents, if they use software that "infringes" on a local software patent? I do understand that if I was a citizen of such a state, I'd have legal problems with releasing such software, but the question is strictly about the end user.
Is there any difference between proprietary and open source applications?
Lastly, and I don't know if it makes a difference, but I am not talking about stealing source code, but engineering something that has been engineered over and over again, until someone happened to patent it, not necessarily and usually not the first one to think of it.
EDIT: Care to explain those anonymous downvotes? No constructive criticism? Or is it just genuinely a bad thing to be concerned with your customers?