load the browser on your n900, navigate to the download link I posted and download the file from there.

By default this will save in your MyDocs folder - you will need to move it from there.

Open the terminal - (if you are at all uncomfortable with this you may want to stop now, you are essentially downloading a random file off of the internet and running it on your phone).

enter the following at the prompt (this will move the file):
mv /home/user/MyDocs/demorecorder /home/user/demorecorder

then (to make it executable)
chmod +x /home/user/demorecorder

now you can start it with
/home/user/demorecorder

hth