And they removed the apache licence. There is no CLA afaik.
A couple alternatives, though both seem to have their flaws:
Shouldly: https://github.com/shouldly/shouldly
TUnit isn't really a fair comparison, it's another test runner like xUnit/NUnit/MSTest, but with more focus on performance/extensibility, which it achieves by using .NET's new test platform :)
Note that AFAIK .NET's new test platform currently only available in C# Dev Kit in vscode, which has different license than "C#" extension