DaFont is a massive archive where many independent designers publish their work. Most fonts on DaFont are "Free for Personal Use." You can find several Blackriver variants here. Simply select the "Free" filter, download, and unzip. Pro tip: Always read the "Readme" file inside the download.
There are a few different things this could refer to, so I want to make sure I give you the right info: Blackriver by Letterhead Fonts (LHF):
Google Fonts, FontSquirrel (checked for 100% free licenses).
A: Only if you have a commercial license. A blackriver font free download for personal use does NOT cover client work.
Various "free for personal use" or "open source" fonts found on sites like DaFont or 1001Fonts that share the name. Could you clarify which specific font creator