The Splunk Add-on For RSA SecurID does not have a modular input. Its an app that expects a sourcetype of [rsa:securid:*] to be available.
This is a syslog format input.
So to circle back to your question, you dont have to use UDP514 for ingesting this. You can use a syslog server to collect the logs and then a use a input to read the syslog files. Or you could move the UDP input to a different port and use that also.
Splunk best practices would be to use a syslog server, and then ingest the files into Splunk by using an monitor on the file. Better control and more redundancy for you.