This user agent was in the middle of many page requests in my Apache logs, requesting content referenced by link tags in the head section.
After a bit of research on one of the link tag URLs, I ran this script:
In almost every case, the requests came from large organizations - corporations, government agencies, and the military.
These institutions often use proxy servers, and Mozilla/4.0 (compatible must be a common user agent setting for the proxy server requests.
In the one case where it wasn’t a large organization, it was a blacklisted IP, and the user agent was Java.
The sample set was limited, but the pattern was clear.