If I set the platform for a J2SE project to the JDK 1.3 that comes with MacOS, the compile fails - javac 
does not understand "-source" and "-target".  Not sure what the deal is - older versions of java on mac 
were based on MSVM, maybe they were using a different javac than Sun's for that release.

Anyway, some workaround should be done for this case - there are very real use cases for using 1.3 on 
mac (applets, 1.3 had hardware graphics acceleration and 1.4 doesn't...).

init:
deps-clean:
Deleting directory /Users/tim/Cal/build
Deleting directory /Users/tim/Cal/dist
clean:
init:
deps-jar:
Created dir: /Users/tim/Cal/build/classes
Compiling 4 source files to /Users/tim/Cal/build/classes
javac: invalid flag: -source
Usage: javac <options> <source files>
where possible options include:
  -g                        Generate all debugging info
  -g:none                   Generate no debugging info
  -g:{lines,vars,source}    Generate only some debugging info
  -O                        Optimize; may hinder debugging or enlarge class file
  -nowarn                   Generate no warnings
  -verbose                  Output messages about what the compiler is doing
  -deprecation              Output source locations where deprecated APIs are used
  -classpath <path>         Specify where to find user class files
  -sourcepath <path>        Specify where to find input source files
  -bootclasspath <path>     Override location of bootstrap class files
  -extdirs <dirs>           Override location of installed extensions
  -d <directory>            Specify where to place generated class files
  -encoding <encoding>      Specify character encoding used by source files
  -target <release>         Generate class files for specific VM version

BUILD FAILED (total time: 1 second)