We have a few shared Macs at work running 10.6.8 and I'd like to disable only the Close & Minimize buttons for one application, not system-wide. I've already re-assigned the keyboard shortcuts for this application inside of the Prefs pane so that the common combos won't work, but I'd like to prevent clicking the buttons also.
If you're lucky, the application uses .nib files for the main window. If that's the case, you should be able to use XCode to edit the .nib file and change the window properties so it doesn't show a close button.
To do this, right-click the application in Finder and select "Show Package Contents". Then navigate to Contents > Resources > some_language.lproj and look at each of the .nib files.
Then double-click the one that looks likely, if you have XCode installed you should then be in the editor view. Disable the window controls and save.
You can remove language .lproj folders other than the language you want to use, so you don't have to repeat the process for all languages the app supports.