What is OpenRocket?
OpenRocket is a rocket model simulation software, it was written by Sampo Niskanen.
This is an open source project hosted on sourceforge and written in Java so that it can be run on all operating systems.
It is totally free and as with any open source project, development is done by a team of volontaires.
For more information about OpenRocket check the official web site and the technical documentation.
You can also suscribe to the development mailing list so that you stay up to date with development progress of the application.