You need the Java Runtime Environment (JRE) I'm pretty sure, but it's been a while since I've messed with Llanfair.

Edit: OP was deleted.

It’s been so long since I’ve messed with Llanfaire that I don’t remember much about it’s build process at all.

If you’re looking for an alternative, you can either use the browser version of LiveSplit called LiveSplitOne or you can run LiveSplit itself through Wine.

Some games may require splits to be submitted along with the run (although this is rare, but always check the rules of the game), but in most cases splits are nice for viewers so they can know your pace. Or for you for that matter so you can know your own pace. Myself personally, I don’t use splits. I just use a flat timer because splits make me anxious when I’m on a good run, or agitated when I’m on a bad one, so I personally don’t like to see them when I do my own runs.