A couple people have asked why it’s only for CC2015, though. There are two big reasons:
Credits Are Due makes use of the new sourceRectAtTime() expression method. I love this feature: it lets you access the dimensions of layers with dynamic borders, which makes it possible for the text layers in Credits Are Due to know how much space to leave for their neighbors. The script essentially works by measuring all the layer heights, spacing things out accordingly, then scrolling the parent layer. (There’s also a cameo by my favorite little expression hack, setting posterizeTime() to a super-low value like .00001. This lowers the expression’s effective framerate to almost nothing, so you get live updates when the comp is edited without having to recalculate layer dimensions on every frame.)
But sourceRectAtTime() was added in the most recent update to After Effects CC2014 (13.2). So why can’t you use that version with Credits Are Due? Well, you can render your credits in it. But if you try to edit them, you’re gonna have a bad time. Every layer in the comp needs to scroll, so as soon as you add a new one that’s not yet linked, you’ll spend most of your time clicking through “expression disabled” popups. Even more fun: manually re-enabling all those expressions once the new layer’s been added to the scroll.
However, CC2015’s new expression handling means things Just Work. Expressions re-enable themselves automatically as soon as they’re able. No more popup error windows. I could probably add a bunch of checks to skip non-scrolling layers and make the math still work, but I want to keep the code to a minimum — expressions can be slow to calculate (though they do seem faster in 2015), and a couple hundred layers into a project you really start to notice. Temporarily disabling the scroll during setup seems a small price to pay for faster playback — particularly when you have a client standing over your shoulder making changes.
tl;dr: new stuff in CC2015 makes Credits Are Due work in a way that won’t make you want to stab yourself in the face. Which, when you’re already stuck making a credit scroll, is important.