We always list what versions of Dreamweaver a product is compatible with under the features tab > system requirements section of our product detail pages on our website.
And you are correct in your assumption. CSS Sculptor Version 1 came out a couple years ago and would have been supported by Dreamweaver 8. If you purchased it before CSS Sculptor 2 came out, you can still access it from the Download Center.
We typically support the latest version of Dreamweaver and one version back whenever we come out with a new product or a new version of a product. We also support 2 versions back if a product is released shortly after a new version of Dreamweaver was released, like in the case of CSS Menu Writer (you can see all 3 versions are supported).
We don't break compatibility with older version of Dreamweaver. In fact, a lot of the functionality probably works with older versions. However, we do not test on older versions so we can't guarantee that.