is Delphi cross platform?

not if you use the "official" proprietary version.

but for those who use Delphi for development a lot, there is good news:
http://freepascal.org/
has a splintered project:
http://lazarus.freepascal.org

that provides the older Delphi ui and toolkits, in cloned code.
uses the lcl [ Lazerus Component Library ] but they worked hard to have the project duplicate the functionality, look and feel of Delphi / C++ Builder 6 / Kylix

So now Delphi [ pascal / object oriented pascal ] has a cross platform implementation, with RAD dev tools that work look and feel the same across the platforms.