DocumentDB vs MongoDB

From AWS gives open source the middle finger:

Bypassing  MongoDB’s licensing by going for API comparability, given that  AWS  knows exactly why MongoDB did that, was always going to be a   controversial move and won’t endear the company to the open-source   community.

MongoDB is hugely popular, although entirely  for the wrong reasons in my mind, and it's kind of hard to scale it up  without infrastructure expertise, which is why it makes sense for a  company to offer some kind of a turnkey solution. Going for  compatibility rather than using the original code also makes a lot of  sense when you're an infrastructure-oriented business, because your own  code tends to be more tailored to your specific resources.

But in  terms of how-it-looks, after having repeatedly been accused of leeching  off open-source, this isn't great. One of the richest services divisions  out there, offloading R&D to the OSS community, then, once the  concept proves to be a potential goldmine, undercutting the original?

The  global trend of big companies is to acknowledge the influence of  open-source in our field and give back. Some do it because they believe  in it, some because they benefit from fresh (or unpaid) eyes, some  because of "optics" (newest trendy term for "public relations"). I'm not  sure that being branded as the only OSS-hostile name in the biz' is a  wise move.