The first 30 days gives you complete access to the software except for the subdomain / SSL certificate generation. After 30 days you can use the software for up to 4 cameras for free.
# Ubuntu / Debian systems make sure curl AND sudo is installed (apt-get install curl sudo)
sudo bash -c "$(curl -s https://dl.bluecherrydvr.com/scripts/install-unstable)"
Once installed, connect to the newly installed server with a web browser (https://bluecherryserver:7001)
Default login: Admin Password: bluecherry
Install the Linux client: sudo apt-get install bluecherry-client