Months ago I worked on a project that required Nmap on the Android™ platform. The project itself was not successful, but I decided that the Android™ Market needed a dedicated Nmap for Android™ app. It was a difficult decision, but I chose to charge a fee ($2.99) for the app if downloaded through the Market and make the source code available to all. My reason for doing so if that paid apps see much fewer users who are more vocal in reporting bugs and developers are more eager to fix these bugs.
Since then my app has been downloaded a few hundred times and I respond to user e-mails on an almost weekly basis. I generally post an update once a week. These updates contain bugfixes as often as they contain new features.
A huge thank you goes out to the Nmap team and to the users. It is the users, who e-mail their bug reports and feature requests frequently, that drive development forward.
2011-03-06: proud to announce a new major feature - a subnet awareness tool. I'll be very interested to hear any/all feedback on this tool. I think it'll be useful to all you wardrivers out there (Screenshot, Source).