Since we started having a beta version of geomorph on GitHub, we understand that installation has become a little bit more complex. We were also aware of the issues for Mac Snow Leopard users.
I have written a detailed summary of how to install geomorph via Package Source or GitHub Source on the new geomorph.net Installation Page.
These instructions allow the most recent geomorph version to be available for users from Mac OS10.6 (Snow Leopard) to OS10.10 (Yosemite). Windows users are also covered (including the quirks of installing on shared computers).