You can get the header files via Subversion access:
svn checkout svn://svn.berlios.de/codeblocks/trunk/src/sdk
Also, you will need ask Killerbot for his import libs if you don't want to go through the pain of extracting them from the dlls.
Another (possibly easier) option is to checkout the complete Code::Blocks source tree (not just the sdk subfolder), build Code::Blocks yourself, and use your own libs. These will likely not be binary-compatible to Killerbot's, but for development, that's not an issue.
This option has the advantage that you don't mess with your development version of Code::Blocks, so even if your plugin crashes and burns, you can still edit sources and compile without needing to move or delete any files (which can be quite annoying).