Liberty Wireless has a website: www.libertywireless.com
I think that they are a subcontractor of Sprint and through them you have access to the entire sprint network; which is nationwide coverage. Just like you can get inexpensive land line coverage from companies that use SBC or AT&T equipment, you can also get inexpensive coverage from cell phone companies who use other cell phone companies’ networks. It's more flexible because, for instance, Liberty Wireless did not setup the Sprint network but through FCC laws they have access to it.
Many cell phone companies consider roaming to be anything outside of your calling area, but as Sprint has a national network, and Liberty Wireless uses that Sprint network; roaming is a mute point. I like it because they have very simple up front plans that you can change anytime that you want.