morning 11, last evening 27, as you can see live count on their website near top. Check Top50 link there on right, seems quite healthy server.
Download is super easy to find, orange button on top left (the top one of the two), then on next page click another such orange button at bottom. The other orange button on home page is for registration - on next page click the blue button at bottom left (zarejestruj sie - Register) and on next page orange button 'Agree' to EULA (Akceptuje) - next page change 'Jazyk' drop down menu from Polski to BEnglish and you are set.
I tried to register but never seen such stupid captcha, couldn't pass it on several tries (its English, lang is not a problem), well, all I can say, F 'em, the installer goes into the bin, I am not mir3 fan anyway but if you are, see if you will fare better. My guess is, the game is not translated to Polish, just pple in game will speak it but I would suppose would also be capable of passable English, likely even better than is mostly seen on this forum :wink-new:
if as you said you are for grind in old caves, then DZone is none of that by a long stretch, its stripped down pure level fest server, new item set every twenty levels, rinse and repeat kind of gameplay (pple can always argue its also got some old caves and its grind too in its own way but its two different worlds really).
I'd say if you don't mind low user count, try out Artificial 'Phoenix' server