Found some interestingly described JBDS 3.0 and earlier downloads in the CSP.

Steps to repro:

1. Log in here: https://www.redhat.com/wapps/sso/login.html

2. Click "Red Hat Network Preferences" -> https://rhn.redhat.com/network/my_account/my_prefs.pxt

3. Click the "Download software" icon/button on the left-hand side of the site:

4. Observe list of downloads - CTRL-F to search for Developer Studio

https://rhn.redhat.com/rhn/software/downloads/SupportedISOs.do

5. Click on one of the entries, such as "JBoss Developer Studio - Portfolio Edition for Linux ", and get here:

https://rhn.redhat.com/rhn/software/channel/downloads/Download.do?cid=9103

"ISO Image Downloads

NOTE: By downloading this software, you agree to the terms and conditions of the applicable License Agreement (available at http://www.redhat.com/licenses/)

Not sure how to download and use these images? Check out our ISO Download Help.
Latest Release

Below please find the complete set of ISO images for the latest release of JBoss Developer Studio - Portfolio Edition for Linux. Depending on the variant of JBoss Developer Studio - Portfolio Edition for Linux you'd like to install, you may only need a subset of these discs. (more information) "

6. Have a WTF moment as you consider how a jarred installer can be classified as an ISO image.