What I'm trying to do is provide for when a user "registers" on one website they are automatically registereed on all af my websites.

In addition, I want to have articles that are accessable to all websites and when you change/edit an article on one website I want it to be automatically changed on all of the websites.

Can this be done?

I've purchased the JMS multisites and have it set up, and it copied all the users/articles over to the new websites (slaves), but when you change/edit an article or a new user registers on my master site, those items are not updated on the slave sites.

First, the concept of JMS is based on the sharing and not on the replication of data that require synchronization.

With JMS, it is possible to share the users between websites.
In this case, the MySQL users tables, will be shared between websites.
As we share the MySQL user tables, this mean that the data is unique and therefore does not need to be synchronized as by definition it is shared and identical for the
websites.
We also have the possibility to partially share the users.
See also
www.jms2win.com/en/joomla-multisite?page...52&category_id=1
www.jms2win.com/en/tutorial#jms12x-16

Concerning the "article sharing for JMS", the concept is to read the article that is present in the website where it is written. Again, we do not duplicate the article.
See
www.jms2win.com/en/joomla-multisite?page...47&category_id=1
tutorial.jms2win.com/joomla/multisite-12...ingforjms/index.html

YES, this is possible with JMS.
You can share the users with JMS.
Concerning the article, you also need the article sharing for JMS.