OK, thanks.
Perhaps an idea might be to sell different features and "addons" to the basic Kiosk software for additional money.
For example.. the basic kiosk software works and everything is good. But if you want to enable the "advanced" features (like ability to enabled/disable specific drives, change colors of timer, whatever, etc..) then this could be an extra $20 purchase.
I have no problem with that sort of license system -- and I think you should be paid for extra work that you are doing.

Perhaps an idea might be to have the basic LITE version.. and then sell the PRO version for an extra $25?
For example, see my own software here:
http://www.snippetmaster.comI give away the free LITE version, and it works perfectly for about 90% of my customers. Then I have about 10% who want extra features, and so I have the PRO version that they can by for about $25.
This works very well... the trick is to make the free LITE version work for "most" people...
I hope that helps.