I tried uploading a template to the open source demo and it didn't load first I got 'website coming soon' message, tried again later thinking maybe i'd caught them at the minute they were reloading the demo and nothing happened at ALL..and I did install AND go to settings and make that the template. not sure if it was the template or the demo?
If there is no page available WB shows the "Under Construction" startpage. Have a look now, there is a page available.
cheers
Klaus