Dear Dan,
All the Magma stuff including the magma seaside that you were looking for is contained in the squeaksource repository: "MagmaTester"
To access this use "World Menu > open...." > "open monticello browser".
Click the "+Repository Button" and select HTTP as the type of repository. The repository access is as you will find on SqueakSource.
MCHttpRepository location: 'http://www.squeaksource.com/MagmaTester' user: '' password: ''
Once this has been accepted you can select this repository and click "open" to browse all of the packages.
To be honest I am not sure what all of them do, but MagmaTesterLoader appears to be the mother package containing most of the rest.
You will also need Magma Seaside in order to use seaside, but the version on squeaksource does not work with the latest Seaside. The version attached to this email does. I have also updated the example store Magma-Seaside-ExampleStore so that there is a test application that works.
Finally I have attached an optional package with some environment fixes as described on the wiki (but not included in Magma so it seams)
We are eagerly awaiting new releases of Magma, and I myself am very close to releasing an implementation of persistence for Pier. I think the combination will be very powerful.
hope this helps
best regards
Keith