According to a blog post on the main Uploader homepage, all Uploader pages, RKS included, will be going through a full "system renewal." I'm not entirely clear on the details, but future use may actually require registration to the Uploader site. Looking at the agenda, the preparations will begin on April 22nd with the actual switch being made on the 29th, so if there's anything up there you want to grab hold of before the wipe, I suggest you do so now. Keep in mind that the posted dates are in reference to the current time in Japan, so it is my suggestion that you grab whatever you want or need by April 20th, if you can even access it.
With the way things are looking, I may simply cease use of the RKS Uploader altogether and have any further entries for challenges be sent to the Grollschwert e-mail account. However, we'll continue to keep an eye on things for whatever may get posted there.