Downloading html files isn't against the rules; however, running code on a website using the engine won't get you too many points from the jury.
Using DLLs without posting the source is ok only when:
a) They aren't yours, but they are well known and don't contain any other resources;
b) I get to overwrite them with the latest version from their website, in order to make sure that they aren't altered or replaced with something else.