The archives contain (1) the Jtwixt Twixt game analyzer program, (2) a small library of 24x24 Twixt games (file twixt_lib_1.tgt), and (3) documentation.
[The following is for Windows. I assume that Unix users are clever enough to adapt the instructions to their platform.]
(1) Unzip the archive. There should be a files named Jtwixt.jar, twixt_lib_1.tgt), README_twixt.html and other documentation files.
(2) Install Sun's Java Runtime Environment. 1.3 (latest version) and 1.1.8 (an older version) are both known to work, at least for some people. (Unfortunately, both are known to not work for other people, so if the first one you try doesn't work for you, uninstall it and try the other one.) Last time I checked you could find both versions here.
(3) If you installed Java 1.3, you should be able to double-click on the Jtwixt.jar file. For Java 1.1.8, run the command line "jre -cp C:\some_folder_names\Jtwixt.jar TwixtGameTreeApp", where "C:\some_folder_names\ " is replaced with a full or relative path name to the Jtwixt.jar file.
On a Mac:
(1) Unstuff the archive (you'll need Stuffit version 5 or higher). There should be a files named Jtwixt.jar, Jtwixt (the Jtwixt application), twixt_lib_1.tgt), README_twixt.html and other documentation files.
(2) Make sure you have MRJ (Macintosh Runtime for Java) 2.2 or higher installed.
(3) Run the Jtwixt application (double-click it).
If anyone is interested in working on the library, please let me know.
I work on a Macintosh, so there may be some glitches getting things to run on Windows or Unix. If you have problems, let me know and I may be able to help.