This branch, with url 
   http://svn.gna.org/svn/pism/branches/stable0.1
is not maintained.

If you want stable0.2 or later, do
   svn co http://svn.gna.org/svn/pism/tags/stable0.2 pism0.2
or similar.

If you really want stable0.1, at least use the tags url:
   svn co http://svn.gna.org/svn/pism/tags/stable0.1 pism0.1