I'm still on Lion, and recently noticed that a lot of my apps are being updated with Notification Center support. Since I'm not on Mountain Lion and therefore don't have Notification Center, I won't be able to use these new features. However, I do have Growl, and was wondering if there is some tweak or hack that I could use to forward these notifications to Growl instead. Thanks in advance!
For Mountain Lion
Hiss goes the other way (sends Growl notifications to the notification centre in Mountain Lion).
Growl 2.0 is on it's way and they've developed a new piece of code they call MIST which will send notifications:
This means if app developers use this code instead then people still on lion won't be unsupported. Read more here http://www.macrumors.com/2012/06/13/next-version-of-growl-to-add-notification-center-support/
Update to ML when you can, it's awesome.
I don't think there's anything (right now at least) to turn notification centre alerts into Growl alerts.
Anecdotal answer, but in my experience the apps that are being updated to support Notification Center are the ones that have always found notifications to be a useful part of the app anyway, and as such they have often supported notifications via other methods, usually Growl. It's pretty much the apps that always supported Growl that are being amended to support Notification Center, usually in addition, not as a replacement.
I doubt very much that anyone will ever bother to write a hack to forward NC notifications to some other system, but there's no reason technically why is may not be possible, it's more financially would it be worth it?