Locking a user/customer to a certain app / tab...

Thats just the standard redirect if you use the standard QB login.  Best bet is to have the people save the app home page as a bookmark.  Or if you have the link somewhere they are clicking, make that link to a specific app.

Sorry, no real good way around it.

Understood, thanks for the clarification. Let me back up a step then: The primary reason for this change is that the app was set up for our business by an individual. The "My Apps" tab says "My apps in johndoe". Our goal was to either hide this tab entirely from customers or change the text to our business name (as opposed to an individual's name). Would changing this text be a possibility or is it linked to the account that created the app? Or (as you previously mentioned) would simply updating the URL be the most logical route? Thanks.

I'd recommend contacting your account rep at QuickBase and they can start the process of changing your account url to www.yourcompany.quickbase.com

That will take care of the confusion that might come on the "my apps" tab.  

Be aware that if you have any code pages or custom url buttons, they might need updating... depending on how they were built to start with.