The source code for mod_tidy is available under the terms of the Apache Licence, Version 2. The Tarball of the latest production source is always available at the Main mod_tidy download area and here.
Windows Binarys (Win32) of mod_tidy are available at the Main mod_tidy download area resp. here.
Most recent RPM packages of mod_tidy for Novell SuSE Linux/OpenSuSE Linux are available at the Main mod_tidy download area resp. here.
Official RPM packages by Novell SuSE Linux/OpenSuSE Linux might be available from SuSEs FTP Server or one of its various mirrors.
In addition to different Novell SuSE Linux/OpenSuSE Linux versions, the RPMs should be easily adaptable to other RPM based systems.
Note that mod_tidy RPMs have several dependencies, you'll have to get at least the following RPMs from Novell SuSE or OpenSuSE:
All the necessary RPMs are either included in the Novell SuSE/OpenSuSE distribution(s) or might be available at the Apache directory on SuSE's FTP Server or at one of its various mirrors or may be dropped some day. RPM repositories like PBone.net also are mirroring SuSEs FTP servers.
To install the RPM packages, use of an automated package management tool, such as Yast2, apt, yum or up2date is recommended but not mandatory.
mod_tidy RPM packages for Fedora Linux might be available at Fedora Extras or RPM repositories like RPMfind.net and PBone.net. These repositories also might hold mod_tidy packages for Mandriva (formerly known as Mandrake) Linux. Because these Repositories just mirror other resources, their mod_tidy packages may be not the latest, depending on the refresh cycle of their index.
A mod_tidy port for FreeBSD Unix is offered by the Ports-Collection.