Hmm, at one point wasn't there a tight integration between Koding and GitLab? Or at least an attempt to make the tools more cooperative?
In fact a Koding acquisition by GitLab seemed like a no brainer.
FWIW ~2012-2013 there was Cloud9, Koding and Nitrous. Now that Nitrous is defunct and Cloud9 was acquired I'm not sure what fills the void.
Put differently is there a void to fill? Is there an actual demand for web IDE's? Or is this just bling?