I understand you're looking for a reliable source or discussion regarding JasperSoft Studio 6.6.0 — but I want to be upfront:
Troubleshooting Performance: Since users have reported performance issues specifically with version 6.6.0, this Community Forum Topic offers tips on increasing RAM allocation in the .ini file to improve speed. jaspersoft studio 660 download link
Download: Select the package matching your OS from the links above. I understand you're looking for a reliable source
Language Feedback: Visual feedback was added to notify designers when they are using deprecated report languages. System Requirements visit the Jaspersoft Community Download page.
Mac
https://sourceforge.net/projects/jasperstudio/files/JaspersoftStudio/6.6.0/TIBCOJaspersoftStudio-6.6.0.final-macosx-cocoa-x86_64.dmg/download
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Current Community Edition: For the latest stable version (currently 7.x or late 6.x), visit the Jaspersoft Community Download page.