Not a bug: The drush @foo.com generate-makefile command may not work on some systems.

You have to specify target directory where you have write access to be able to use command like 'drush @foo.com generate-makefile ~/static/make.txt' because otherwise it will attempt to write it in the foo.com directory where only Aegir system user has write access. If you will specify only filename without correct path, it will trigger the mysterious 'Error: Call to undefined function drush_make_error()' which doesn't even exist in Drush, by the way.