This seems like a step away from "ridiculous" to me.

Declaring something as 1.0 means that any 1.X releases are going to be backwards-compatible with the 1.0 spec.

This is objectively different than versioning something 0.X, which implies that the baseline spec is not finalized.

Calling something "Beta", however, just means that a feature-complete major version is still being actively developed (i.e. new minor features and bugfixes).

In other words "1.0 Beta" just means "Stable spec, active codebase".

So why is it called "1.0.1" (and now 1.0.1 on the homepage) and not "1.0.0-beta" ?

The 1.0.0 release was called 1.0.0 - there has been a patch release since. Pretty much any software I can think of lists the latest release on the homepage rather than linking to a static version, but you're right it's a little confusing that specifying a version in the querystring doesn't actually appear to link directly to that version.

EDIT: confusing if the intention of the iojs team was to have the querystring actually mean something... they may well not have that intention, in which case meh :)

My point wasn't about the patch version it's about the software being called "beta" while the version doesn't reflect that at all.

If the api is fixed and its just bug fixes before release why isn't this 1.0.0-beta or -rcN, with a 1.0.0 (a vanilla version is always considered higher than one with an identifier like "-beta" or "-rc1"

Sure, but that's more of a reflection on the convention (some might say 'rationality' ;) of associating a single vector of 'production status' with a number beginning with 1. Again, this is a semver thing, not an iojs thing.