Don't use any scratch dir, handle write-protected installation

script/server

@@ -7,9 +7,13 @@ then
     echo "Mongod not started"
 else
     mkdir -p -v log/thin/
-		#force AGPL
-		tar cf ../_source.tar -X .gitignore *
-		mv ../_source.tar public/source.tar
+    #force AGPL
+    test -w public -a ! -e  public/source.tar &&
+        tar cf public/source.tar  --exclude='source.tar' -X .gitignore *
+    test -e public/source.tar || {
+        echo "Can't find, or even create, public/source.tar. Giving up"
+        exit 2
+    }
     bundle exec ruby ./script/websocket_server.rb&
     bundle exec thin start $@
 fi