The installation procedure is currently disabled to avoid data loss on the user's harddisk. It might be enabled in the future but it is not planned yet. However, note that there is a clone feature that allows you to create another live USB (see the tools folder on the Desktop once booted). There are security checks to ensure that the clone can only be done on another USB stick, but it can be bypassed by opening a terminal and running /opt/clone/clone.sh /dev/sdX where sdXis your hard disk (this command-line bypass also allows to clone on multiple keys simultaneously).
• this is not a usual distro install, in particular, the system will remain in a single squashfs file and unless you use the keep feature, it is not intented to be upgraded (an upgrade will consist in another similar clone operation with upgrade selected)