Which Technology should I use for developing a Rich GUI based desktop Application?

[mihirp]

We are planning to make a commercial GUI based software (for both desktop and mobile) targeting individual users. We plan to have good web 2.0 like rich application features (Google like dynamic auto suggest, drag and drop, browser based look and feel etc) and lot of user controls (trees, grids, etc).

1. Wanted to know which is the best technology suited for such a software - Java, .NET, Adobe, Opensource etc?

2. Which one has best Rapid Application development tools?

3. What are licensing costs w.r.t development IDE, client tools/framework etc as well as royalty based costs associated with distribution of software.

4. What would be the best database option available for such software. We are looking for databases which have decent functionality and not royalty based distribution costs associated with it. e.g Mysql has licensing costs associated with commercial distribution of software. Should postgresql be used as its free to redistribute with your commercial package as well.


Thanks and looking forward to some helpful insight.