Redmine UI discrepancy

I am choosing between Trac and Redmine. Leaving dogma out (they use Python and Ruby, resp.) I'm test-driving both to choose based on the usability of the UI.

At the outset I'm seeing a discrepancy between a demo of Redmine

and the view that I get when I install Redmine and launch the server locally.

Where is the difference coming from?

The first screenshot above is from Planio, a hosted Redmine service. Some time ago, they've rolled out a custom, more modern design for their customers.

At the time, Planio published a blog article about the design goals and the process.