wmarcy

I have Featured Content Sliders all over my forum, works like a charm.  
 

​Yes, you can !

 

Installed like a dream!  Thanks again and sorry for being stupid.

​Thanks, glad to hear you think so. Maybe I should charge more  . 
Coming out with a new version that runs as a separate widget to get around that cache issue. Hopefully be out soon.

One of the best apps I have bought for my forum!

​As @Adriano Faria mentioned, anything you can do with a stock IPS board, you can do as a collab owner. So as a collab owner, you could create a forum inside your collab and make it invisible to all except yourself.
​In order to invite somebody to your group, they must first be a member on the site. This is because the site administrator ultimately has authority to decide which member groups can join in collabs, and a user without an account does not have a member group. Therefore a user must first be processed into the community, and then they can be invited to a group/collab ( according to their permissions by the site administrator ).
As for receiving an email, the invitation is sent through the core IPS notification system so the user can choose the method by which they are notified of invites ( email/inline/etc. ).
​There are a couple of ways to tackle this. One way would be to assign members to a new member group (or secondary group) when they purchase a product in nexus. Then you could give permission to that particular group to create collabs in your category(ies) of choice. You could also assign a maximum amount of collabs they can create in that category (via the category settings), or across the site in whole via the ACP under the member group settings.
Another way is to use my Rules Application to create collaborations for them automatically when they purchase certain products via nexus. For example, you could write a rule such as "When user purchases product X, if payment has been received, then create a collaboration for them in category Y". However, the Rules application is very new and I haven't yet released the expansion pack for the Commerce app which will allow you to tie into commerce events, so you'll need to wait a short time for that to become available.
But to answer your question, it can be done and you have options!

Kevin this looks very useful and quite involved, which is why I am waiting to buy it until I see a few use cases that make sense for my forum. 
I look forward to hearing how others are using it.