v4.0.3 compatibility

Is dhtmlxForm v 4.0.3 compatible with older versions of dhtmlx. I ask because I have v.3.0 of the suite and downloaded form v4.0.3 and now all my attached forms fail with:
Uncaught TypeError: Undefined is not a function
when making the call similar to:
prodForm = layoutprod.attachForm();

It works with Form 3.6

These versions are not compatible. Plus some 4+ components are based on new engine, some were changed in css