If a company does not wish to honor refunds, they or their reseller need to tell the consumer about it at time of purchase. I used to work in the building trades and I had to do a some returns. But I did them anyway because it was the honest thing to do. I was the one that told the customer the product I was selling was suitable for the task at hand. So it was my responsibility to make it right when it turned out that I was wrong.
Liability is a bit trickier.
I certainly wouldn't want to submit a big fix if it means I have to go to court over it in the future. But commercial distribution of Open Source software is another matter. The commercial distributors are the ones claiming the software is suitable merchandise. If they wish to disclaim all merchantibility, they need to convey that information to me before I purchase the software. I have next to me a commercial Open Source operating system.