I have been thinking alot about what was mentioned in an earlier thread about how dewed is always searching for inspiration and drive to work on this dew-new phplinks project and how the lack of compensation has been bringing up questions about making some of the scripts upgrades/features and mods only available for a monetary exchange. I think there is (unfortunately) something worth while in that thought and I have some ideas about how this may work...
these days many sites offer a free service but also make available to many users the ability to upgrade their account to "pro". This pro or paid account enables the user to take advantage of many more features available through the site or software for example; flickr.com, picturepush.com, pandora.com, launchcast.com, etc.
This may or may not be a good option to get users excited about using the website or script then if they want the "full" or pro features that come along with the service, they would pay for it. Maybe this would be a yearly subscription or whatever but I know I would sign up!
Just a thought and it seems much easier than keeping track of the accounting side for paying for and receiving fees for each upgrade option or whatever.