ZChecker is a really neat addition to any Zope/Plone-Developers toolkit for QA... especially if you've got mxTidy installed, because then it can check your pagetemplates for XHTML-validity. However, mxTidy's setup script won't run successfully on Mac OS X without modifying its own mxSetup.py, because it otherwise won't pick up necessary libraries due to missing paths. Here's a diff, of the file adding those paths, for your convenience. Note, that the paths are specific to Darwin Ports, as that's what I use. Fink users will probably need to modify the paths to something beginning with /sw.

--- -	2006-10-02 14:45:13.000000000 +0200
+++ /dev/fd/63	2006-10-02 14:45:13.000000000 +0200
@@ -309,7 +309,7 @@
 # compiler and linker for include files and libraries. LIB and INCLUDE
 # are environment variables used on Windows platforms, other platforms
 # may have different names.
-STDLIBPATH = build_path(['/usr/lib', '/opt/lib', '$LIB'])
+STDLIBPATH = build_path(['/usr/lib', '/opt/lib', '/opt/local/lib', '$LIB'])
 STDINCLPATH = build_path(['/usr/include', '/opt/include', '$INCLUDE'])
 
 # Add additional dirs from Windows registry if available
@@ -324,9 +324,9 @@
 # Default paths for additional library and include file search (in
 # addition to the standard system directories above); these are always
 # added to the compile and link commands by mxSetup per default.
-LIBPATH = build_path(['/usr/local/lib',
+LIBPATH = build_path(['/usr/local/lib', '/opt/local/lib',
                       os.path.join(sys.prefix, 'lib')])
-INCLPATH = build_path(['/usr/local/include',
+INCLPATH = build_path(['/usr/local/include', '/opt/local/include',
                        os.path.join(sys.prefix, 'include')])
 
 verify_path(LIBPATH)

Tip o' the hat to Andi a.k.a. witsch for this... Andi, you really need to get your own blog, come on! ;-)