The distribution here includes source for the Edinburgh Speech Tools Library and Festival itself. Voices are also provided for US English, other voices are available on the festival site and instructions to build new voices are given here.
Although we agreesively attempt to run Festival on all platforms we can get access to it is not always the case that it works out of the box. The hardest requirement is probably having a working and compatible audio system, simple as audio is supposed to be in our experience we find a wide range of standard to utterly bizzare support for this. We do give pointers and support for dealing with non-standard audio systems but its not always easy for us to do.
The system is written in C++ which means with every new version of of each vendor's C++ compiler that is released our system probably wont compile without minor changes. We try to keep up with new versions as quickly as we can, and make patches or instructions available for new versions as soon as we can.
You will need both speech tools and festival source to compile and also at least one lexicon and voice. These sources compile and run under most Unix systems and Windows.