I am no lawyer or anything related, but I know a lot about the topic at hand. I recommend to take all I write with a grain of salt :).
This is how it works:
All things you create in sketchup, which will later be commercialized in any context, will be illegal. It doesn’t matter, if you import it into blender and run it through different programs.
Now here are things you have to consider:
If you make a donate button, which implies that they support YOU with their donation, it is legal. But if you write that they will receive something, if they donate (like the sketchup object), you unknowingly make a contract and it is considered commercialization. Then it is no donation anymore.
When you import the objects from sketchup into your program and use them as references to rebuild them with the blender tools, you can legally charge money for it, because you made them from scratch with blender. But you can’t modify or edit the imported sketchup objects and charge money for it, because they originally came from sketchup. It is a pretty murky area, because some things can be transformative, but that is another discussion.
The short answer is: You can’t sell things, which originally came from sketchup. But you can rebuild the same mesh from scratch with the blender tools and sell it.
- All these things can happen. It is google’s responsibility to prove that you used their software to make these meshes. And this is frankly overkill. You would need an impossible amount of man power to hunt all these users down, who uses their software illegally. It probably won’t happen that you get problems.
So my advice: If you can live with an uneasy feeling about them finding out that you use their software and break their TOS, go ahead. But if you want to be on the safe side, you should consider using blender in the first place and drop sketchup or maybe just use it as a quick prototype/sketch engine to make references for blender.
I hope I could help.