Take a look at the software forum, to get an idea of what is available.

IS Boxer is the top option around, imo.
And HKN is the top free option, and is a strong option too.

Keyclone is a one-time fee for a lifetime license, it has great key broadcasting and can round-robin but doesn't have a lot of features compared to other options.
GCP and PB are other subscription software options, but you'd need to google to find more information on either.
Different options to take a peak at, but neither is close to IS Boxer.

Similarly you can go with Auto Hot Key or Octopus as other free options.