1.- Dave: Oxwall already haves jquery in the core: 

https://developers.oxwall.com/ow_static/plugins/base/js/jquery.min.js

2.- Tammy: You can't say that "everything" doesn't work.

If doesn't work then you wouldn't be able to load the website.

I agree that there is a lot of problems that need to be fixed, if you really had that number of members i think that you should had hire a developer in that moment instead of complain in this place, and i know that you can get a lot of money with that amount of users, money that can be used on hiring someone competent enough and right now you may had a million users.

3.-If you are having js problems, you should send a screenshot of the Google Chrome developer Console or Firefox console, not just the Warning message.

4.- Development takes time, is not something that you think and it magically happens.

5.- You cannot have it all for free, if you are having a lot of issues, and you already had that amount of users, you must consider to hire someone to develope your own custom website. Think that facebook is the number 1 not for complaining but for hiring the best developers.

6.- We cannot say it is everything ok because is not. I can try to make it better. But I don't like lies, so I'm not gonna tell you if or when I can fix something that I haven't started yet.

7.- This is not personal, your personal differences haves nothing to do with the fact that if we do not communicate in the right way, you can not expect to be taken seriously anymore.

Now on topic:

Right now it cannot handle a million users without core modifications and plugin modifications, so i think that if you want 1 million users, you have to expend not just on the server, but in the core itself too and modifications on the current plugins.

Now about the solutions.

As I already said, the main problem is js related, every time that I refresh my website, it loads hundreds of ajax get querys. I think the main problem is in the newsfeed and mailbox plugins.

About all the MySQL querys, it is not really a big deal, the server can handle a lot more stress.

Tammy: I haven't seen your website, but you may have all your problems in the javascript.

Ryan - that is a loaded question.  It depends on the server and many other factors that could effect performance. 

However if i had to take a stab in the dark here with my past experience and seeing other sites perform in the past, i would guess that on a shared server, somewhere between 3-10 thousand.  On a VPS or Dedi of course that number jumps significantly. 

But remember that many factors play into these numbers. 

If it were me and i had the motivation, talent, desire, and the money to strive for a million member site I would put together a team of pro's, server admin, programmers, and social experts and code my own site from the ground up.  If your going to play with the big boys then you need big toys. 

Some people might ask why "social experts"?  Because they can tell you things that you never considered. Things that places such as Las Vegas have known for many years.  Like what colors or blend of colors makes people feel a certain way, what makes someone want to click on a button or try something they never have before, and most important if you are in it for the money is what makes people give up their money in exchange for something else.  If you cant convert what you have done or what your doing into cash then its not a business its a hobby.