Hello,
they 've removed the option to download it some time ago. Wiki is also not available anymore. Maybe writing to support or someone of the moderators or cd projekt red staff will help. You are not the first one.
I know as much as you... why they have ........or when red kit will be or won't be availiable again... nothing.
Nemo
Edited:
Redkit is one of the Witcher 2 bonus materials so you should be able to download it from your steam/gog/whatever you are using.
Hm,
thank you I did not know this, because I downloaded it 3 years ago...
Anyway,
it is available again on the Red Kit site, maybe even without registration to any forums.
BUT You must use the smaller button at the top. The link for the site is
http://redkit.cdprojektred.com/en/download