Using Memberstack 2.0? There is an updated version of this article here.
"Hello! I'd like to ask if it's possible to install two MS scripts on one website?"
Yes and no. It's technically possible, but we don't recommend it. Placing two scripts on the same is not possible.
Things will start to break if you have the header script installed twice on the same page. This means you can only install two scripts if you create two entirely distinct membership areas on your site.
You would need two signup & login pages (each with different scripts in the header) and members will need separate accounts to log in to each area.