The exrun script is in this repository, It's also in the current shipping tarball. It should also be in the source RPM, which contains the tarball.

Since these are the only source artifacts this project ships, and version 3.1.0 is about <i>nine</i> years old now, you might not even even have the normal fallback available to you, which is to contact the person who built the package you are using.

I'd recommend just upgrading to the current version, which should be upwards-compatible from 3.1.0.