seam.properties is just a properties file
components.xml allows you to set properties and configure many other options as well
As for why it doesn't work. I assume you have the getters/setters provided. Ff not this will need to be added. Additionally, I had to make a copy of seam.properties and place it in WEB-INF/classes/ folder of the war. I don't know if this is a requirement or not but that was the only way I was able to get it working. I just left the seam.properties in the jar empty.