Meaning of Beta

Beta - does not just mean that it's fast and free
nor even that it has bugs.

Some teams use alpha and gamma tests (I am sure delta's exist somewhere as well)
Here we usually mean Public Beta - meaning one used by some real customers.

I think the best meaning concept is that this Public Beta defines a stage where the software is good enough to use, (perhaps with restrictions), but that while the Supplier (rather than a purchaser/user) decides what issues should be enhanced or fixed, real user feedback and experience is obtained.

In a fully released product (whether commercial or open source) there is a formal or implied commitment to support the advertised functionality, and this places some restrictions on the development team in how they alter and maintain the existing behaviour.

So in a Beta an API might be altered with little palaver, but after Beta we'd expect more warning and backwards compatibility.

Of course all of this is relative to market or community understanding - Google's gmail is now almost three years old - and still describes itself as Beta in its logo. And while we expect reliability it may not be promised - and our expectations are still set by the description and the price.