If you want to run this project in a virtualenv to isolate it from other Python projects on your system, create a virtualenv and activate it. Then run bin/install-reqs to install the dependencies for this project into your Python environment.
You'll need a PostGIS-enabled PostgreSQL database available for this project; create it with a command like createdb -T template_postgis mlt. See the GeoDjango installation documentation for more details on setting up PostGIS and a PostGIS template database.
You'll probably need to create an mlt/settings_local.py file with some details of your local configuration, including, most likely, your database name and user (unless they are both named "mlt"). See mlt/settings_local.sample.py for a sample that can be copied to mlt/settings_local.py and modified.
Once this configuration is done, you should be able to run ./manage.py syncdb, then ./manage.py runserver and access the MLT in your browser at http://localhost:8000.
To install the necessary Ruby Gems for Compass/Sass development, run bin/install-gems requirements/gems.txt. Update requirements/gems.txt if newer gems should be used.
In addition to the above configuration, in any production deployment this entire app should be served exclusively over HTTPS (since almost all use of the site is authenticated, and serving authenticated pages over HTTP invites session hijacking attacks). Ideally, the non-HTTP URLs should redirect to the HTTPS version. The SESSION_COOKIE_SECURE setting should be set to True in settings_local.py when the app is being served over HTTPS.
This app also uses the new staticfiles contrib app in Django 1.3 for collecting static assets from reusable components into a single directory for production serving. Under "runserver" in development this is handled automatically. In production, run ./manage.py collectstatic to collect all static assets into the collected-assets directory (or whatever STATIC_ROOT is set to in settings_local.py), and make those collected assets available by HTTP at the STATIC_URL setting.