I'm not a css-crimes-doer ([insert rant about how back in my day we had the font and center and table tags and we LIKED it]), and I avoid using JavaScript as much as possible, but since it doesn't look like anyone else has answered (at least, in a comment),
First, about why the script widget doesn't work on other websites: what does it look like? Is it trying to run JavaScript from Crowdfundr's website? Because if memory serves, modern browsers block that kind of thing for security reasons. But also, Cohost doesn't allow the script tag anyways, so if the widget uses it, it wouldn't work even if it wasn't blocked by the browser.
But really my best suggestion would be to ask the Crowdfundr people if they can make the preview show the funding status, perhaps by including them in a hidden block at the top of the page. To be clear, I haven't tested to be sure Cohost would show stuff in a hidden block, and you would really want to test it before asking (or find out from someone who already knows), because if it doesn't work it would be a real waste of their time. Or you could ask if they could make a URI or ?thingy that shows just the funding status, so you could embed both that and the regular URI in your posts.