Yes, we got a little better response on the 5.1 release than anticipated, so their database got mad and revolted. @Morgan_Hardwood was able to get that holding page up so at least it doesn't 404.
It's likely to be updated this summer at some point to hopefully alleviate this problem as RawTherapee rockets upwards to world raw editing domination (the yin to darktables yang?)!
I blame all of the Pentaxians looking for that sweet, sweet Pixel Shift editing.