Has http, have https?

Has http, have https? http://hosting.gmodules........

Can I still use the gadget if I want to collect something like DL numbers because the http gadget doesn't matter because the form itself is https?

It looks like the gadget is not available using the https protocol. Regardless of that, the gadget URL itself does not appear in the Google Sites page, so you should be able to use it.

You can also try embedding the form using the Iframe code.

Complete Guide: Getting the Form iFrame Code