MDruzgala,
I'm not a lawyer so my input is simply my basic understanding, so if I am wrong feel free to post.
This has always seemed a question that in some aspects is simple to explain while yet in other aspects it may not be.
My understanding is that te biggest issue is how the data is being pulled in and utilized. It is illegal to hack Google map tiles and import them into your application directly as a service, unless you have permissions to do so via whatever license it takes. I remember a few years ago you could purchase a Google image server and install it as part of your overall GIS server solution, thus allowing you to use their data inside your application. I don't know if this is offered anymore or not. Likewise, Arc2Earth use to offer an application for a fee that did the same within ArcGIS Desktop software. Again, I don't know if its currently available either.
The application or widget in question on this thread does not pull the data into the Flex Viewer as a service, but instead pulls it into a separate shell with the appropriate logos and terms of use, etc.
Having said that, I'm not a lawyer and its typically safer to default to not using their data if you have any doubts. There appears to be multiple threads regarding this, but everyone seems to make a statement without adding additional supporting explaination, etc.
Again this is only my understanding and could be totally wrong....