To summarize:

For everyone else, use this blog post as a map to find your legacy installer, then immediately start planning your migration to JasperSoft Studio or the native REST v2 reporting API.

Before attempting to download version 4.0.1, it is important to note that iReport Designer has been officially End of Life (EOL) for several years. Jaspersoft (now part of TIBCO) has moved all development and support to TIBCO Jaspersoft Studio .

: On Windows, it is often best to install iReport directly under the C:\ drive (avoiding "Program Files") to prevent permission-related bugs.