Google has now made public Waves accessible to those without a google account. They are ‘Read Only’, but you can now, at least view them. (Interaction other than simple copy function and some minor formatting changes does require a Google account.)
From the Google Wave Developer Blog:

We recently introduced a new API for embedding waves, which includes a powerful new feature: anonymous, read-only access to public waves. Prior to this launch, webmasters could embed waves into their sites, but visitors could only see the content of the embedded wave if they had a Google Wave account, were logged in, and had access to that particular wave.

As you can see by the image above, there are some issues with choosing the smaller, sidebar friendly widget. Below, you will see a larger widget that helps solve these format problems.

» Read more: Google Wave widget…No account necessary