Project-O is what you want. It is open source with HTTP reachable via LSL scripts that use local host.
It uses WAMP or LAMP and php with low impact.
What it adds to your NPCs is real AIML backend chat and functions you can embed codes to trigger your npcs with depending on the replies (use basic ALICE set) to start.

Start here https://program-o.com/
then https://github.com/Program-O/Program-O/tree/dev
Set it up as it says (real easy) btw.
just keep it all local host since we arnt using it like a web page here but you can to both.
I already have LSL scripts that work great interfacing my NPCs to program-o (opensource btw).
I will post a few examples after you have the basics set up.
But this is the good stuff and mort (dev of project-o) is great.
They just have no idea how cool what they have is for 3d spaces.
Anyway i will post more about the how to later.
NPCS get real AI, god help us all! lol
This lets you put your NPCs into the very real AIML A.L.I.C.E world and that has its own learning curve where the idea is to have AI talk and act as human as a computer can.
As you can use program-o to make it how you like, your AIML set can be done to talk about and know about and learn about your idea (your 3d space).
I will not go into that, Just about how you can hook it into your mad dream within your own region.
And no it will not effect anything as far as the grid goes because it becomes a sub system as backend to just your sim.
Anyway take a look and ask alot of questions here and there but it is the good stuff !
tnx (more to come)

It doesn't appear to be self-learning.

Ask it who is God, and it will reply master of the universe. Tell it He Man is master of the universe, and it doesn't then equate He Man = God.

I've been running ALICE bots in OSgrid since 2010. https://www.pandorabots.com/botmaster/en/home 2 of them, hooked into my Pikkubots http://pikkubot.de/dokuwiki/doku.php. They appear like AV's, not NPC's. You can chat and even IM them, and pikku can do tons of stuff, despite them being in opensim raher than SL. It are paid clients tho, so an open source replacement is great. It's nice stuff to play with, only writing your own XML's is a bit of a tedious job.

Well, for me i wanted a back end AI that no longer depends on 3rd party at all other than your own services and OSG with your region.
I tried other solutions and found more problems than are needed since your own scripts become the middle ware and at the same time have full control over all aspects.
With some php modifications and embedding your own AIML triggers added to what your bot will say, it gives endless possibilities.
For example i may say something to my AI bot about how nice the chair is and it may say Oh may i sit on it too?.
Because i have embedded an extra command in that reply (not seen in chat) the bot will sit on the chair if i tell it that it is okay.
The embed codes or triggers are held in the AIML and you can add as many you like.
It takes a big load off of LSL scripts and complexity and at the same time puts the embed commands where they match to the AI replies (like do a dance for me) or whatever.
The php can also be changed to further enhance NPC actions.
In the end this is a lot more than just a chatter bot since you can set actions as well as words in a logical way.
Anyway it is more than just push/pull AI chat.

Well some changes to all of this, Mort passed Program-O on to umm someone thats good at nothing. LoL
Its still all good but we can do what they cant here.
BTW (Mort is fine and cure worked for the big C and is happy fishing in rl)
Now what?
Well i want to set a goal post and call in the best i know and make it an add-on to core!
Yah i see you running away there lol.
Thing is i still have not found a better back-end where YOU own it all.
I have spent 2 years working it out as to how to blend AIML (core process) into something anyone can use.
Thing is im not as good as you so i need help.
What it can do is add to our simulations a new way to meld rl and this.
If AI can be embedded into our VR life and it does learn, Why not?
For now, if you have skill and interest then beep me.
I can do it alone but by the time im done ill be dead!
If any of this sounds cool no matter who then chime in and lets do this OSG style
add Otan Tau to your list of ok and i will talk to you more about it.
TNX (OSG dont run on wishes, takes money!)