I was able to locate one of the US gimp mirrors. (Bad of them to have their main download site down, their mirrors list unavailable, and the same site serves their mailing lists.)
http://gimp.mirrors.hoobly.com/gimp/
I think this is a legit, up-to-date mirror of the gimp.org downloads, but if you download software from a mirror you should verify the checksums from gimp.org.
The downloads you listed above are source code, not help files. The linuxfromscratch stuff you found does not seem to be the actual Gimp help files, so that won't help here. Either get the help download from the mirror I found, or you can follow saulgoode's steps to build the help system yourself. What you are looking for will unpack into HTML files; if you got XML files you have the wrong thing.