Yes these classes are reliant on other classes which are ClassAct compatible. We are in the process of creating a brand new set of classes now. Currently working on tickbox.gadget to replace checkbox.gadget and that is almost completed on OS3.
This class is using the H&P window.class from OS3.9 so we do not have access to the source code for that. We will be looking into other solutions.
The InfoWindow Class Wiki page has now been updated for OS3: