We've made the source code of our web client available (idea's for licence to use appreciated).
We've also made available our Python client library GLIBSE, which is configured to work out of the box with our test GLBSE server.
The test server is for everyone to use and playwith, to look for vulnerabilities, or to have a server to practice their own development with it's all here.
Currently there is very little documentation, so you're best looking through the source but it's something were working on.
The test servers api urls are not the same as the live server, it is what we will be moving our live server over to in the near future.
Tech details here: https://gitorious.org/black-market/pages/Home