Side-By-Side is a good app for viewing two different web sites, well, side by side. As is "sling Note" (IMHO; link here:
https://itunes.apple.com/us/app/sling-note-web-clipping-easy/id385068849?mt=8). Both allow you to see and do more than you can with the stock Apple apps.
But.
They are not the same thing as Quasar. The two apps I mentioned allow you to do multiple things within the app itself, only. You're not really seeing two or more different apps running on the iPad, the app has got multiple windows.
With Quasar, you can actually have more than one app open such as a calculator app, a web browsing app and a word processing app. So, that' styrene different apps at once. Again, the others are only one app with multiple functions inside.
So, there truly is a big difference between Quasar and anything else. Quasar is true multi-tasking along the same lines as a computer where you can open
and view multiple programs/apps at once.
I know the developer has put a lot of work into Quasar and it works for those who want to use it. But, if you're not a jail breaker (or can't BE jail broken at this time), the other apps might do in a pinch.
Hope this clarifies.
Marilyn