What is the difference between iReport and Jaspersoft Studio?
Both are tools for visually designing reports and both come from the same vendor.
Why is Jaspersoft pushing two similar technologies?
Answer
In the FAQ of http://www.jaspersoft.com:
Why is Jaspersoft Doing this?
For years our community of developers asked us to support the Eclipse platform due to its popularity and capabilities. This feedback made the decision to build an Eclipse-based report designer easy. Jaspersoft users will benefit from the rich capabilities of the Eclipse platform and Eclipse developers will benefit from a complete open source BI stack to build and deploy their reports. We also aim to create a report design environment that is both powerful and intuitive so that it appeals to both the advanced and the first-time report developer.
So I think this is simply a fork with the goal to provide the designer as an eclipse based application.
Plus they also provide the designer as a plugin version for Eclipse:
Which Eclipse releases does Jaspersoft Studio work with?
The plugin version of Jaspersoft Studio can be installed on Eclipse IDE 3.5 or later. The compatible Eclipse releases are Indigo, Helios and Galileo.
Anyway I could not download the Jaspersoft Studio to give it a try because the download page does currently not exist.