The source is at bzr branch lp:~fallenpegasus/drizzle/awss3. Pull it and build it like you would the main Drizzle. The engine is built-in, no need to plugin load it.
CREATE TABLE colors (nam VARCHAR(32) NOT NULL PRIMARY KEY, val BLOB) ENGINE='AWSS3' CONNECTION='awss3 bucket_name aws_id aws_secret'; SELECT val FROM colors WHERE nam='BlueViolet';
I will try to keep it tracking the main Drizzle dev tree.