Plugin not found: ["acts_as_list"]

I am trying to install acts_as_list in a rails 2.2.2 project but when I
try the following: ruby script/plugin install acts_as_list

I get: Plugin not found: ["acts_as_list"]

I had to download the acts_as_list plugin from the github because it
isn't included in Rails 2.2.2.

The files are in my vendor/plugins/acts_as_list folder so I have:

lib/active_record/acts/list.rb
README
test/list_test.rb
init.rb

What am I doing wrong here?

TIA

if the plugin is already installed in vendor/plugins there is no
reason to install it with script/plugin.