Is the Hashicorp Vault App on Splunkbase a free app or is there a fee?
It is a free app in Splunkbase, though it does mention it is for Vault Enterprise Users. It leverages opensource collectors. (telgraf and fluentd)
More here:
https://splunkbase.splunk.com/app/5093/
https://www.hashicorp.com/get/vault-splunk-application/
https://learn.hashicorp.com/vault/monitoring/monitor-telemetry-audit-splunk