I'm not sure what messages you are referring to. Can you post a screenshot?
There is a "Donate" button on the window that Tunnelblick pops up when a new version of Tunnelblick is available. The window will appear each time you launch Tunnelblick until you either update to the new version or check the "Skip this version" checkbook (or is that a button, too? I don't remember.)
I don't think recent versions of Tunnelblick ask for donations other than that, so a screenshot would be helpful.