Here's the problem with that: most people will use this (I assume) only once or twice, to, say, create instructions for their web app (like commented above), and would be happy to pay 20/40/60$ for the software, but there's no reason for them to buy a subscription. Unless you're aiming at an audience that creates instructions multiple times a month?
You obviously haven't heard of e-learning industry. These kind of tools are used very regularly by e-learning professionals, and instructors. Sometimes everyday. (How do I know this? I was doing e-learning for a few years.) But this tool faces a stiff competition from established and more sophisticated tools like Adobe Captivate, Camtasia, http://www.sameshow.com/
To add to this line of thought, charging per video made would be the way to go. You could limit the free version not only with the downloading and branding options, but also with the length the of the video (eg. max length of free video 30 seconds).
Be careful about pushing too hard in this direction. Non-paying users aren't getting a totally free ride (more below), and you don't want to give them a bad feeling about using your service.
Since the cost of hosting a non-paying user is actually pretty small (particularly because these aren't videos -- they're screenshots), if you have a non-paying user who embeds their useful walkthrough in a very visible location... well, that's pretty damned valuable free advertising. They've more than "paid" for the service, and you really want them to have a good feeling from the transaction, not shame them -- if they feel good about using the walkthroughs, they'll use them more, and not only evangelize but also find themselves needing the paid features... and be happy to pay for them, not forced against their will.
Actual freeloaders (people who are only using the free service in low-traffic places, or only internally) cost you almost nothing to host, so it's not smart to obsess about them.
The trick instead is to draw the right line between free and premium, and also work out how to structure pricing to account for many different kinds of uses.
I get the name, but don't you think something that is easily digestible by people would be less of a risk? It can't be a good thing if you have to explain how to pronounce it to people. Don't handicap yourself with a risky name.