The full Macintosh source code is available in a separate archive. It is called POVMAC_S.SIT (or povmac_s.hqx up on the internet.) It should be in the same directory as the other POV-Ray program archives... if it is not, complain to the sysop or network administrator, or better yet, search it out yourself on the internet:
http://www.povray.org/ or
http://mac.povray.org/
Why is it separate?
The main reason is that, as you can see, POV-Ray version 3.1 has grown considerably in size, and the source code makes it even bigger. Most people use POV-Ray as-is for rendering images, and do not need the source code. So it is available separately for the programmers who want to learn about POV-Ray internals, or add/modify features of POV-Ray itself.
Please read the POVLEGAL.DOC before redistributing unofficial custom compiles of POV-Ray. It is allowed with certain restrictions. Also, feel free to submit your changes to the POV-Ray team for inclusion in future versions... this is how POV-Ray has grown to be as great as it is, with your help!