The DEMO version only includes 4 pages:
http://ugtg.org
http://ugtg.org/spip_page-contribuer.html
http://ugtg.org/spip_page-themes.html
http://ugtg.org/spip_page-auteurs.html

It is possible to download these free files and install them on your server, so you can test how the site works.
Visit https://www.waybackmachinedownloader.com/en/buy-wayback-machine-downloader-recover/ to buy a fully functioning site.
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