I tried testing this plugin -which is awesome btw- on a more recent sourcemod version, before I was running it on 1.8 and now, 1.10. It still works even without compiling it. On linux.
The problem is, GeoIP databases are not updated anymore and the last one is quite outdated now, from February.
A manual workaround would be nice, I can suggest 2 sites where I found some legacy material and somebody could tell us which one is the right one to upload: