The great thing about Android is customization. Making your device your own by changing UI elements endlessly. The problem with customizing with Android devices is that there is no one place for Android themes. N3xGen Theme Manager has been developed to change that. It is an app which collects themes for ADW, LauncherPro, Go Launcher and CM7 all in one place for quick and easy access.
Like any community, it needs people for it to grow. So the developers have made it easy for people to add their own themes and you can choose if you want to give them away for free or charge.