When UMeng cloned Flurry, I could be wrong but I don't believe we did anything, and I'm pretty sure that was the right call. Any lengthy legal dispute will distract you from other important things; legal disputes that are likely to go nowhere are likely to distract you for no benefit whatsoever.
I empathize - I was a bit annoyed by the first version of UMeng, which was a pretty close copy of Flurry's web design and feature set. But if your situation is anything like ours was, you'll see the companies evolve away from each other over time as you each adapt to your respective markets - and you probably didn't have the staff and cultural knowledge to support the Chinese market anyway.
I empathize - I was a bit annoyed by the first version of UMeng, which was a pretty close copy of Flurry's web design and feature set. But if your situation is anything like ours was, you'll see the companies evolve away from each other over time as you each adapt to your respective markets - and you probably didn't have the staff and cultural knowledge to support the Chinese market anyway.