Now that the .NET 8.0 preview is out, many folks will want to experiment with it and possibly run tests under the TestCentric GUI. A newly released extension, the .NET 8.0 Pluggable Agent, makes this possible.
NUnit 2.0 through 2.7 was delivered as an all-inclusive package: test framework, console runner and GUI runner. With NUnit 3 that changed. The framework and console runner became separate packages and the GUI was no longer developed.