Make sure clean_theme is installed. Another requirement is nodejs and less that should be installed on the server.

Install npm and nodejs packages

• Modify the sources.list-file on wheezy-systems to be able to use apt-get to install nodejs.

  • nano /etc/apt/sources.list deb http://http.debian.net/debian wheezy-backports main

• Run apt-get update to reload the sources.list.

  • apt-get update

• Install nodejs

  • apt-get -t wheezy-backports install nodejs update-alternatives --install /usr/bin/node nodejs /usr/bin/nodejs 100

• Install curl, since the npm script uses this.

  • apt-get install curl -y

• Install npm using wget

  • wget -O install.sh https://www.npmjs.org/install.sh --no-certificate-check sh install.sh

• Install some dependancies using npm

  • npm install -g less less-plugin-clean-css 

Once this is done you should upload your theme unzipped with a tree as following in an addons folder:
theme_bootswatch
--- static (dir)
--- views (dir)

--- __init__,py
--- __openerp__.py
 

After doing this, restart your server, go to settings, click update module list. You should now be able to find your theme, without an error.

I am running this theme on odoo 8.0 at widows 7. 

Is the addons folder properly specified in your .conf file? Did you update your modules list? 

As a sidenote: this theme seems to work only for the master branch, when trying to run it on 8.0 it results in an error.