Hmm, looking for MMORPGs can be tough these days to find active ones, especially if you're thinking about private servers.
For classic MMORPG vibes with potentially active private servers, you might want to check out games like Ragnarok Online. There are quite a few private servers for it that keep the community going.
If you're open to something a bit more modern but still with a strong community feel, maybe look into Guild Wars 2. It's not subscription-based and has a pretty dedicated player base. Or, if you want a truly massive world, Black Desert Online is known for its graphics and combat, though it can be a bit grindy.