What exactly is installed on this RP614? Is it still the same OS that came with the device, or is it something installed since then? I did a search and saw some references to uClinux, which very well could have been what was installed initially. I ran across a site that had installed a custom firmware image on this firewall/router, but that hadn't been updated in five or six years. The tarball of the source code wasn't available from the link they offered, either. uClinux is still out there, though. Eh, here's the
web site.
Regarding cron, although I can't say I have looked, I'd be surprised if that is something compiled into the kernel. It is a daemon that runs in the background that runs a series of scripts at scheduled times.