You could have downloaded PolSARpro 4.0 from our software library for free. The most popular versions among the program users are 4.2, 4.0 and 3.0. The program belongs to Development Tools. The actual developer of the free software is ESA.
From the developer:
The Polarimetric SAR Data Processing and Educational Tool aims to facilitate the accessibility and exploitation of multi-polarised SAR datasets including those from ESA Third Party Missions (ALOS PALSAR), Envisat ASAR Alternating Polarisation mode products, RADARSAT-2 and TerraSAR-X.
You may want to check out more software, such as PBDoc UNICODE Including PB10.5 & PB9.0.2 VM, GpProfile or Developer Express Refactor! Pro, which might be similar to PolSARpro.