If you want to contribute, here's what you need to know:
Join dev at tortoisesvn tigris org by sending an empty email to dev-subscribe@tortoisesvn.tigris.org
Please search the archives before posting.
Get the HEAD trunk at http://tortoisesvn.googlecode.com/svn/trunk with TortoiseSVN.
Set up your environment so that you can compile TortoiseSVN. Have a look at build.txt in the project root folder to know what you need to download and how to setup the directory hierarchy. Do your
changes, test your stuff, create a patch with TortoiseSVN and send the patch to dev at tortoisesvn tigris org.
If we love your work, we will sooner or later give you direct commit access to the repository :-)