You just need to read what's written on Web pages paying more attention! The source code is now on Google code, here:
http://code.google.com/p/tortoisesvn/[
^].
Get get source, you will need Subversion. Here is how you can check out:
http://code.google.com/p/tortoisesvn/source/checkout[
^].
You can do it with installed TortoiseSVN, but you don't have to do it. You need to download Subversion itself and use its console-only application the way it is show above. You don't need to install this application; you can just copy all required files in some directory and run. And, of course, you can build Subversion console client from source.
—SA