Marek Olšák, a leading independent developer within the Mesa community, has pushed a number of bug-fixes into libtxc_dxtn and has found it worthy of declaring the 1.0.0 release. Unfortunately due to patent issues, this S3TC library will remain external from Mesa for the foreseeable future and will not be finding its way into any major Linux distribution. Only the source to this library is also distributed but no binary releases will be made. By the end-user compiling the source-code, you assume the legal liabilities and risk.
This external library is supported by many classic Mesa and Gallium3D drivers, including R600g, for dealing with S3 Texture Compression that is needed by many modern OpenGL games and applications.
"It is highly recommended to use the latest version of the library to prevent graphical corruptions caused by any older version when using S3TC textures."
The announcement was made on the Mesa mailing list and there is the FreeDesktop.org Git repository.