I am currently working on a small update to the MacOS X/9 version of CMask. So far, I think that I have fixed almost all of the shortcomings in the GUI from the previous release. The "Generate Score..." command should hopefully now allow you to open any file on MacOS X 10.4. And the other menu commands are all working with the exception of "Page Setup".
I should have a test release ready to go sometime tomorrow. I don't want to make another public release though until I am sure that it works on 10.4 correctly. So, I will be contacting a few people and asking them to test it for me. If you are interested in testing the new Cmask before it becomes public, please send me an email in the next few days via the contact form (and put "CMask" in the subject line). I am looking for someone to try it on 10.5 Leopard too.