Eco Lab compiles out of the box on OSX using the Mac OSX Dev Tools package, which is available for free download from http://connect.apple.com You will also need a copy of TCL/Tk - the ActiveTCL works well, although building TCL/Tk from source is also possible. If you do the latter, choose the unix build directory, not the macosx one.
You need to make a choice whether you want to run Eco Lab as a
native Aqua application, or as an X-windows application under the
XFree86 server software. Specify
--enable-aqua on the Tk configure line to build for Aqua,
rather than X11. On the Eco Labbuild line, specify
the make command line.
You may also use
build the prerequisite packages. Eco Lab's Makefiles will search for
Macports software located in
/opt/local prior to searching
system locations. Note that if you install the MacPorts version of Tk,
it uses X11 only, Aqua mode is unavailable.