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.