If you don't want to use the self-hosting package then click the View HTML button in the navigation: 
When you click this button a popup will appear with just the HTML of the form container. There's no HEAD, no BODY, no CSS, no JS. 
You can download the formstrap HTML (which builds on the Bootstrap 5.3.5 standard), Bootstrap 5.3.5 HTML or Bootsrap 4.6 HTML.
formstrap HTML
This is just the HTML of a formstrap form. You will need to provide any CSS you require and also Javascript to process interactive aspects of the form (e.g. page navigation, user-driven events, replicable containers, validation, submission etc).
Bootstrap 5.3.5 HTML
This is the same as formstrap HTML but all proprietary formstrap functions (e.g. replicable containers, "other, please specify", form validation and submission etc) and CSS classes are removed so the only dependencies are the Bootstrap 5.3.5 CSS and JS files. Variable width input-groups components are not supported in Bootstrap 5.3.5. Two column radio/check lists are also not natively supported.
Bootstrap 4.6 HTML
This is the same as formstrap 5.3.5 HTML but certain backward incompatible features are either removed or reformulated e.g.
- Check and Radio Styling: Bootstrap 4.6 doesn't support displaying radios and checkboxes as Buttons or switches.
- Style: Input controls are not styled by Bootstrap and are displayed using the browser's default styling.
- Gutters: Bootstrap 4.6 does not support custom or vertical gutters. Columns have a default horizontal gutter width. You may need to alter your settings to provide vertical space (e.g. bottom margin) between stacking columns.
- Input Groups: The coding of input-groups is slightly different than in Bootstrap 5.3.5 (add-ons are contained in <div>s).
- Breakpoints: There is no xxl breakpoint in Bootstrap 4.6 so any xxl widths you have specified will be ignored and the highest specified breakpoint (below xxl) will be used.