The is available for download as a standalone application or as a NetBeans plugin. While newer versions exist, this specific legacy version is often maintained for compatibility with older JasperReports projects. Official Download Links
project files, including the necessary JARs and project distributions, on the JasperReports Library SourceForge page Jaspersoft Community: Release notes and historical links for iReport Designer v3.7.6 are available via the Jaspersoft Community knowledge base 2. Installation Methods ireport 3.7 6 download
If your goal is to eventually leave iReport behind, here is the safe migration path: iReport Designer v3