Can customers migrate apps from Open Liberty to WAS Base, ND or Liberty with full fidelity - like they can do now, by taking apps on Liberty and go directly to Base and ND?

Yes. Applications created using Open Liberty can easily be migrated to any version of WebSphere Liberty because the WebSphere Liberty portfolio is built on top of Open Liberty – the codebase of the commercial portfolio includes 100% of the Open Liberty code. They share the same code, but WebSphere Liberty has additional features that are not open source. Applications created using Open Liberty can be migrated to WebSphere traditional Base and ND, but there are a few differences to consider, just as when moving from WebSphere Liberty to WebSphere traditional:  Open Liberty provides an implementation of Java EE 8, which is also available in WebSphere Liberty and WebSphere traditional, that makes the migration of apps that use these features easy.  Open Liberty also provides an implementation of the Eclipse MicroProfile capabilities for building Java microservices.  The Eclipse MicroProfile capabilities are available in WebSphere Liberty, but are not available on WebSphere traditional, so apps that use these features are not as easily migrated from Open Liberty to WebSphere traditional.