We have now started loading the Ontopia source code into Subversion over at the Ontopia Google Code project. So far, what we have is the Java source code for the product plus the tests. We also have a guide to building the code.
This means that you can now browse the code and build the ontopia.jar and the ontopia-tests.jar files.
We are still working on getting the code for the web applications and so on into Subversion. We also need to finish the build scripts to make it possible to build a complete distribution.