I found it clear after reading the page, the “Demo Categories & Shim Details” gives three different options.

In short, canvas is not required, using the DOM is allowed.

I think any local restrictions, beyond the 1024 character limit, would go against the spirit of it all.

> You can submit visual effects, generative art, tiny games, synths, or whatever you can fit into 1KB of JavaScript.

There is no mention of canvas

There is two web technologies shims: HTML and Canvas