I see this case as being different to copying someone's work. I do admit it's a bit morally questionable, in the sense that it's something that Snapchat doesn't want people doing. However, my view of the relationship between Internet services and client software which accesses those services is such that alternative implementations of both should be considered legitimate.

You have raised a very good point though, and it's certainly made me revisit my take on this. I've personally been the victim of others taking copies of my app and selling it under different names (which I obviously do have a problem with). However I've also seen other people implement similar features and a similar UI to my own app, and I don't have a problem with that - we only got to where we are today because of the spread of ideas through these means (see: Xerox PARC and all the companies that have used their work).

In this particular case there was no IP violation. It was simply an alternative implementation of a network protocol - and in fact it was just a library, not an application in and of itself. The only thing I think the author did wrong was to include the API keys.