If multiple users could use the "IDE" at the same time I could move entirely off of GSuite. Right now being able to edit the occasional code block with 4 people watching is worth GDocs.
Almost all of VSCode is open source, but live share is not.. On their website I noticed that they intend to provide generous 'free plans' of live share, which is a big hint about how Microsoft intends to monetize their open source products.
In any case, I see a lot of value for the IDE to be integrated into your git host, so I think this is a great step for GitLab.