"Then she received a letter from a lawyer in Florida,telling her that a) one image web site is not licensed; b) If she doesn't fix it, they'll file a law suit; and c) She needs to pay the lawyers $4,000 to "cover the unauthorised use of the single image without license"."

That happens all the time. Enough that it's fairly well known now. I think few would just lift an image off another site these days.

If this is required to get sites to give a shit about accessibility once again, great! A few headline cases of huge, crippling fines, and few would just put out a site without accessibility, or give a tender to developers without a contract section covering it.

So the only remaining issues are whether $4k is a reasonable sum or just a lawyer trying it on, and whether she can sue OpenCart for providing a non-accessible platform.