Note this link takes you to the existing (expiring in 4 days) RC5 version NOT RC6. I have searched the files area on Sourceforge and RC6 is not there nor on the Princeton site.
I think someone has triggered the announcement too soon!
After the insecure site warning on the site, actually trying to download the link that it says in the RC6 version (32 or 64 bit versions) gives the following error:
The requested URL /pulsar/K1JT/wsjtx-2.1.0-rc6-win64.exe was not found on this server.
The problem has already been reported in the developement lists here
I think it is reasonable to assume that there was something wrong with RC6 and it was “pulled” as there is now an RC7 release here for all the usual platforms: