Hi Maria,
Many people installing from Macports on OSX find:
a) installing xorg-server is not needed if XQuartz is installed, so that "sudo port install demeter" is actually sufficient. Perhaps someone can correct me if they have a different experience.
b) the install does sometimes fail, but installing a reduced selection of the many packages listed as dependencies at a time usually works, and everything gets installed after a few tries. As Prof Gaillard suggested just a few days ago, setting "ulimit -n1024" (that is typing that in the terminal before running 'sudo port install demeter') should help with this problem too.
So, the basic message is: keep trying, perhaps installing a few of the packages at a time if setting "ulimit -n1024" doesn't work.