Digimarc is pricey and embeds an unseen "watermark" in the image. You have to track the image through Digimarc - that works fine for images on the web, but what happens if they just decide to print the images on their home computer?
You can create an action in PS to watermark your images:
It's simple in ps or any program that will let you make layers. make a new layer and add your text - change the layer opacity to 50% or less and merge the layers. If you have PS you can record the steps you take and create your own action. Then you just play the action each time you need to watermark.
I make all my "demo" images the same size - I made two watermark actions - one for horizontal and one for vertical.
As for brand names on discs - I don't know - you can use Kodak or whatever if you've just got an ordinary burner. I use a LightScribe burner, so I have to purchase LightScribe discs.