I hope this license is temporary because this license is non-free.

Subject to the terms of this license, we grant you a non-transferable, non-exclusive, worldwide, royalty-free license to access and use the code solely for the purposes of review, compilation and non-commercial distribution.

note how this explicitly leaves out modification.

You may provide the code to anyone else and publish excerpts of it for the purposes of review, compilation and non-commercial distribution, provided that when you do so you make any recipient of the code aware of the terms of this license, they must agree to be bound by the terms of this license and you must attribute the code to the provider

once again, they exclude modification of the code.

no forks can be made because they aren't allowed to modify the app in anyway.

Additionally, the termination clauses say that they can just terminate your rights to use the code if they feel like it, no other reason needed. This is a direct attack against open source.

by definition?

the Free Software Foundation, the ones that started the whole idea of sharing code as a philosophy of software, do not consider source available as free software or "open source".

It does not meet Eric S Raymond's definition, the one who invented the term "open source".

It does not meet the Open Source Initiative definition either.

Even Wikipedia gives the right definition of open source:

They grant the recipient the rights to use the software, examine the source code, modify it, and distribute the modifications.

So stop defending Rossmann and admit that the app is not open source.