The Libtiff library, which has been a reference implementation of TIFF for many years, has disappeared from the Internet. It was located at remotesensing.org, a domain whose owner apparently was willing to host it without having any close connection to the project. The domain fell into someone else’s hands, and the content changed completely, breaking all links to Libtiff material. Malice doesn’t seem to be involved; the original owner of remotesensing.org just walked away from the domain or forgot to renew it. Who owns it now is unknown, since it’s registered under a privacy shield.
Originally Libtiff was hosted on libtiff.org, but that fell into the hands of a domain owner with no interest in the project. I don’t know why. It still holds Libtiff code, but it’s many years out of date.
As I’m writing this, people on the Libtiff list are trying to figure out exactly what happened. There’s talk of trying to get libtiff.org back, though that may or may not be possible.
For the moment, there’s no primary source for Libtiff on the Web. I’ll hopefully be able to post more information later.