Does anybody know if Zenphoto can be used with Yahoo Small Business web hosting? I notice they only offer MySQL version 4.1

You have to try yourself as we don't test below php5 and mysql 5.

Also note that the next release of Zenphoto will require PHP5. MySQL 4.1 is pretty old. Are you sure they have only that?

From a quick look: For those prices they really should have php5 and mysql 5. Otherwise there are surely better alternatives...