Technically it is not freeware. From there site:

The SNMX program may be downloaded from this site. We license SNMX for in-house and OEM applications with our "SNMX Rapid Development Environment". With this license, you can construct powerful SNMP management applications for your site, product, or end user. You receive:

Note that, without a license, SNMX cannot be redistributed with any hardware or software systems, nor incorporated in any hardware or software platform. SNMX is not freeware, and SNMP Frameworks, Inc. rigorously enforces this rule!

Reading their license it basically says you can use it free to help evaulate it. However, it looks interesting.