I have the new Leopard too and there is no "generate input" option but I did a search on Mac Help, it outlined how to install additional input method:
1. change the extension of the Cantonese file downloaded (or any program you wrote) to ".inputplugin"
[Note:after I have unzipped the downloaded zip file, it shows up a collection of files but they were icon, read me first etc, I only chose and change the file extension of the application file to install, not sure if I need to install other as well]
2. drop it in "library"/"input method"
3. activate "international" and tick the "Cantonese" box
4. log out and log in again
then you will see Cantonese(or the USA) flag on the top menu bar.
So far so good, but the problem I have is, I still couldn't input in Cantonese, I typed in say "hong", it was underlined, but when I typed the next word, it disappeared, no Chinese character came up at all. Whereas, if I choose "pinyin" option (Mandarin input), Chinese characters option would come up.
So I don't know which part of my procedure is wrong, or the CM.zip downloaded is not compatible with OS X10.5 as it was written in 2005 for Tiger.