I had to build something for a client recently. They had one but it was over 10 years old and certain parts had just stopped working. They. like yourself, had also looked but not found anything that would work, and they were willing to pay.
Now do to their absolute lack of any kind of programing skills it is not something that is worth distributing. But it really it isn't to difficult to build one.
Think about it there is 5 basic types of fields; input, select, checkbox, radio, and textarea. So the user selects the type, and gives it a name. You then let them set a default value, and the fields size.
Then to validate is not difficult. In both php and javascript you create a few basic functions, like an email validation function, a password validation function, a length validation function, and a function to check if checkboxes or radio buttons are selected. And you let the user select if they want to validate a particular field or not and how.
Then to validate in Javascript you can loop through elements by their tag name. If an element needs validation you can add non-standard attributes like
<input type="text" id="fieldid" name="fieldname" value="somevalue" class="mycss" data-required="yes" data-length="5" />
These are supported in HTML 5 but HTML 4 just ignores them but javascript can access them with getAttribute.
To validate in PHP is much simpler as you plan to store all the field names in a database, the validation requirements can be stored with them.
Its is quite simple I built the one in just a few days. Of course something a bit more flexible may take a bit longer but it would not be difficult.