I wrote a little summary about installing the SVN version of BlitzMax on OS X from scratch. I hope somebody will find it useful:
http://www.wmaus.net/wordpress/20080810-installing-blitzmax-on-os-x-leopard-from-the-svn-repository/
http://www.wmaus.net/wordpress/20080810-installing-blitzmax-on-os-x-leopard-from-the-svn-repository/