It's because GitHub Pages (where the Brick site itself is hosted right now) runs an outdated version of Jekyll that doesn't support Collections yet.

You can track the issue here: https://github.com/alfredxing/brick/issues/62

It looks like it's supposed to link to the downloadable original source, but it's missing. To use the font just click the little + button and then the 'Bucket' button in the menu.

They're supposed to link to a font-specific specimen page where you can see exactly how the font renders and take advantage of some content-editable headings and paragraphs.