1. Get the sources
I got the source from sourceforge http://sourceforge.net/projects/opende/files/

2. Build ode
My environment are:
export DEVROOT=/Developer/Platforms/iPhoneOS.platform/Developer
export SDKROOT=$DEVROOT/SDKs/iPhoneOS3.0.sdk
export CC=$DEVROOT/usr/bin/gcc
export LD=$DEVROOT/usr/bin/ld
export CPP=$DEVROOT/usr/bin/cpp
export CXX=$DEVROOT/usr/bin/g++
export AR=$DEVROOT/usr/bin/ar
export AS=$DEVROOT/usr/bin/as
export NM=$DEVROOT/usr/bin/nm
export CXXCPP=$DEVROOT/usr/bin/cpp
export RANLIB=$DEVROOT/usr/bin/ranlib
export LDFLAGS="-arch armv6 -pipe -no-cpp-precomp -isysroot $SDKROOT -L/Users/olivier/Documents/IphoneDevProjects/3rdParty/iphone-os/lib"
export CFLAGS="-arch armv6 -pipe -no-cpp-precomp -isysroot $SDKROOT -I/Users/olivier/Documents/IphoneDevProjects/3rdParty/iphone-os/include"
export CXXFLAGS="-arch armv6 -pipe -no-cpp-precomp -isysroot $SDKROOT -I/Users/olivier/Documents/IphoneDevProjects/3rdParty/iphone-os/include/"
export ac_cv_func_malloc_0_nonnull=yes
export ac_cv_func_realloc_0_nonnull=yes

The last two line are important because iphone does not have function like rpl_realloc.

The configure step:
./configure --host=arm-apple-darwin9 --prefix=/Users/olivier/Documents/IphoneDevProjects/3rdParty/iphone-os/ --with-x=no  --disable-demos

Then make, and make install. you are done.