is "Tag post" plugin only MU?

i fell in love with the tag post plugin... but installation say it should be installed in wp-content/mu-plugins and i do not have this directory.

and the post indexer plugin should also be installed, for it to work, but this plugin, also katagorized as "multisite" should be installed in the ordinary wp-content/plugins directory....

1) does some mu plugins go in "/mu-plugins" and other in "/plugins" ?
2) will "post tag" not work on ordinary wp installation?

Best regards per olsen Denmark