Seems to work great with RS 3.1, download works okay. Just a remark, original post says it's compatible with Athens campaign, indeed it does work for most UI elements it but the faction symbols are wrong (Spartan) in at least two locations, as seen here, in all versions I could find:
So far I haven't noticed other (swap) factions with a similar issue.
Just make absolute sure you backup all files involved if you try this out, which is a must anyway, but have the issue with Athens symbols in mind. So far I haven't noticed other (swap) factions with a similar issue, which is good.