Often available for free to developers to implement ECW viewing in their own apps.
appears to be a proprietary software tool (likely for industrial or engineering use, such as compressor sizing or thermodynamics). Offering or promoting "free downloads" of commercial software that isn't explicitly freeware could: ecw compressor 26 free download new
To install ECW Compressor 2.6:
This is where the plugin shines or fails, depending on your needs. Often available for free to developers to implement