The community edition is free to use. The only requirement is to display the logo. Sitefinity does need to do a better job of telling people that on their website. You can also use it for commericial sites now with the logo at the bottom.
They just started this a couple months ago.
To get the community edtion:
Sign up for My Client.net Login then you will be able to access the download section. Besure to select the Community Edition for .Net 3.5 or 2.0. If you download the standard edition it will ask for a product key.
I am able to run the system on my local Windows XP pro with a sql server on another box. However the system supports local sql express and MySql which I have not try yet.
So far I am happy with the product. If I have a client in the future that wants it without the logo, they can pay for the standard version, I only charge for setting it up. The community edition comes with 3 projects ready to use. I quick learn how to set my own project within a day.
If you decide to try it out or have any problems, I can help you out.