I'm looking over the homepage - it's really not clear that nopcommerce is free - lets put some big writing to shout that to people.
+++
Home page
_________
on the slider, it says DOWNLOAD
let's change that to say something like FREE TO DOWNLOAD & USE or CLICK TO DOWNLOAD AND USE
where it says in big text
'Welcome to the official community and development site for nopCommerce'
lets say 'Welcome to nopCommerce - FREE ecommerce solution'
then in the smaller text we can write Welcome to the official community and development site for nopCommerce ... then continue with the existing text in a new paragraph.
+++
I already made some suggestions for the demo page but I would add that where the page header says
'Store Demo'
lets write 'Store Demo - nopCommerce FREE to download and use.
let's not be shy about getting the message across :)
.