FAIB  To clarify, what this tiny app does that the Mac OS doesn't is let you double click to open a dvd rip from the Finder, an admittedly small feature not currently available in the Apple DVD player.

As is evident from the comments, its a small feature, and definitely not something everyone needs. :)

However, it does make firing up ripped DVDs just a touch simpler, which is all it aims to do.  
(Version 1.0.1)

FAIB  Appending the extension ".dvdvideo" will automagically turn the folder into a bundle that PlayVideoTS recognizes for as long as PlayVideoTS is installed on the system.

This is a general feature of the Finder in Mac OS X that allows software developers to specify that certain directories be treated as single files.

It is the same mechanism that drives the ".app" = Application feature. All ".app" Applications are actually folders, in Apple speak "bundles" or "packages", that contain the executables and resources for the Application.

If you would like to explore this feature, try control clicking on an application. You should be given the option to "Show Package Contents". You will now be able to explore the files inside the Application in the Finder. Beware though, because messing up these files can cause the Application to malfunction.  
(Version 1.0.1)

FAIB  Important note for everyone:

The folder dragging feature was accidentally disabled for this release, if you would like this functionality, please visit the website to download a fixed version, PlayVideoTS 1.0.1.

The new version should be appearing on MacUpdate soon.

Thank you to everyone for the feedback!  
(Version 1.0)

FAIB  Hello,

Thanks for noticing that the folder dragging function wasn't working. The feature was accidently disabled during the final revisions. A new release, PlayVideoTS 1.0.1, is available on our website that fixes the bug.

Thanks for the feedback!  
(Version 1.0)