Perhaps it's the responsibility of each website using slider.js to degrade gracefully on their own. That seems more appropriate to me. In which case, I don't mind if they don't bother to degrade while demoing their javascript product.
Are you really demanding that the author of an open source javascript project to supply non-javascript code to make your website backwards compatible? You've gotta be kidding me.
That's not his responsibilty at all. Try contributing to an open source project instead of complaining.
It's very easy to handle a Javascript fallback for Slider.js:
Instead of having an empty container in which your slider will be templated, put the content for the non-javascript into it.
That's it ;)
Just because the Slider Javascript will empty the content of it ;)
(Side thought: maybe I'm wrong, but in 2011, are we still need a JS backwards?)