An ambitious developer, Esten Hurtle, has developed a way to quickly turn any Vine video into an animated GIF using a very simple Mac app. The app, VineGifR, is free and available to download by following the download link in the ReadMe section on Esten's Github page. It's a good idea to follow this page for further app updates as development continues. As you'll see below, the current version of the app is very basic.
The first time you launch the app on your Mac you may run into a warning that the app isn't signed by a developer. To bypass this warning, right-click on it and then click on Open. This warning is part of security settings introduced in OS X 10.8 Mountain Lion.
VineGifR requires only a valid Vine link to turn the short video into a GIF. Once you have the link, you enter it into the only text field in the app and click on "GIF'it." You'll be asked where to save the GIF and to give it a name. The end result is a GIF similar to the one below:
Since the app only requires a Vine URL and Vine itself doesn't offer any type of privacy settings, this leaves any Vine video ripe for conversion. Just be sure to ask permission and all that good stuff before you go creating GIFs out of Vines that don't belong to you.