I have no idea about running an IRC server, and no idea whatsoever about unrealircd, but I gave it a go and built it from source.
The installation seems to be straight forward as the provided ./Config script (yep, not ./configure ) leads one through while holding ones hand (where I've hit ENTER to accept the default for each question asked, except for the target installation directory).
It seems to me that it's best to build it yourself, because it's asking quite specific questions regarding SSL certificates and wants, or prefers, to install to the users $HOME directory. Also their website instructs to not install as root, so I'm not quite sure how to configure it to work well with Core as an extension, if it's possible.
To compile software, you need to install the compiletc.tcz extension.
Depending on the software, possibly some *-dev.tcz extensions, which can usually be determined easily by the error message provided when attempting to build it. It's possible that unrealircd doesn't have any compile dependencies other than those provided by compiletc.tcz . At least I didn't get any errors.