It's a very solo friendly MMO. Private servers are usually for people who want changes to the official game (or removal of changes), and sometimes just to avoid paying subscription fees. This one is aiming to replicate the official state of the game as it was in 2009.

It's mostly a "grind" sort of game with simplistic combat. It's pretty relaxing for the most part, though it does have some tense PvP elements if you enter into some special areas. You can definitely play it fully focused, but most people would conside it a "Second Monitor" game. i.e. You can watch YouTube or do work and keep old-school RuneScape active on a second screen, interacting every minute or so.

There's a large amount of osrs that play "ironman" myself included which prohibits interacting with the economy at all.

This is a trade off for me because I would prefer 2006scape or pre market place economy where you had to buy and sell manually by sitting in an area and trade. Automated trading economy made a lot of the content of the game easy to cheat because a good deal of the Quests and such are really just running around picking up obscure items. With the exchange and the wiki its practically ez scape.