The only way to legally download version 4.1 (or the current version, such as Nik Collection 8) for free is through the official DxO 30-day trial .
You get unlimited access to all plugins, including Silver Efex Pro and Viveza , for 30 days. Nik Collection 4.1 for Mac Free Download
If you are looking for a legal way to use Nik Collection for free, your options are limited to either the official trial or an aging version from 2012. 1. Official 30-Day Free Trial The only way to legally download version 4
While Google no longer hosts the file, it can still be found via Internet Archive (Wayback Machine). including Silver Efex Pro and Viveza