To your question: Yes it is possible to install and use DemoRecorder on a computer which is not connected on the internet.
This is possible because the license-activation process can be done on another
computer with an Internet-connection by using the web-browser.
The license-activation process results in a license-file which can then be transferred to the computer where DemoRecorder runs on. ( e.g. by using a USB-stick ).
DemoRecorder itself including its license manager does not have any network connections.
Also, if you have to move the license to another computer, e.g., due to hardware upgrade, it is possible to do that online by repeating the activation process with the demorec-hostid of the new computer. (The only difference to the original license activation is that you have to confirm online that the license is not used on the previous computer anymore.)
The license activation takes place at the following URL (or by clicking on the "Activate License"-entry of the website-menu ): http://demorecorder.com/licenses/activate.php
Interview on the Linux Link Tech Show. Please select Episode 154.
DemoRecorder featured in Linux-User Magazine (in German)