@
> does your moral responsibility for a free tool you created extend to protecting the customers of a business that profits off your work? Probably kinda yes,
Absolutely not.
The (L)GPL explicitly disclaims any warranty, while also listing "providing a warranty to your customers" as something someone making commercial use of the code might want to do.
B's choice to make commercial use of code from A confers no additional responsibility, moral or otherwise, on A.