Why on earth is this an announcement post?
Anyway this is blown way out of proportion by most casuals. The first version of Project Zanaris will just be rentable servers where you have a configuration file that you can adjust based on pre-defined knobs and dials. This has already been confirmed (both in the blogs/videos as well as by Mod Sarnie in discord).
While they are looking for avenues of allowing content creation by the people renting it, the reality is this is probably never going to happen. There's a reason the blogs were kept rather vague - and Sarnie confirmed that as well. They don't want to over-promise in case it isn't possible, and it most likely won't be possible to go beyond that.
The way I see it, there are five possible "levels" at which this concept could come to life. Note that each level is significantly less likely than the one before it.
1. Just some dials and knobs on a configuration file to enable, disable and modify pre-defined aspects of the game (xp rate, disabling specific bosses, etc). This has been confirmed to be coming in 2025.
2. Ability to use their in-house tools and create novel content that does not touch the existing codebase. So literally just build a completely stand-alone map with your own objects and models, add in creatures, brand new items etc. Cannot use existing models, locs, items etc. This is what they're looking to support in the future, but it is far too early to make any promises. Reality is this most likely requires #3 & #4 alongside, which are extremely unlikely to ever take place.
3. Access to data files (configs, animations, models and so on)
4. Access to the runescript codebase, allowing modifying any existing content.
5. Access to the engine code (Java, C++). Not even most of the J-mods have access to this.
So tl;dr is, when the first version of community servers drops, it will just be #1. The issue is this will completely kill any hype people have over it and likely significantly hinder the future development of this concept in the future. I wouldn't give it very high odds of ever reaching #2, though I'd like to be proven wrong. Until then, however, at #1 it does zero harm to current RSPS. At #2 it will hurt emulation-based servers, although OSRS-emulations don't really exist, so the overall impact is fairly negligible. #2 would additionally result in the tooling reaching current private servers and potentially help this scene out alongside.
At levels #3 & #4 however, servers should start to become worried. That would mean the end of a lot of servers, namely anything oldschool based. The probability of it ever making anywhere close to this stage is slim to none though. There's too much at line to be putting out 1.5 million lines of code built over decades. It would never get past the higher ups.