Yes they are talking about Java applets. However, the technology has improved (a large portion of windows users have a java quick launcher set to run on start up) and if it is anything like Facebook's original "Photo Uploader" (back before they integrated with phones and iPhoto and other apps, they had a Java app where you could browse and add photos. It would also scale/reduce quality of high megapixel photos that otherwise couldn't be uploaded to Facebook -- this was down client side through the app and was still relatively quick.) it won't be so bad.

TL;DR: Yes, it's a java applet. However, if its anything like how Facebook has done java applets in the browser, it will feel quick and lightweight on most systems.