Not sure it helps, but an observation is that Oracle's relational database occupied a somewhat similar role, in that it tied together data from different sources, and enabled cross-platform interoperation. This was very important at the time, because there were several different hardware vendors, and companies didn't want to get locked in. And of course, a whole ecosystem of third-party tools grew up around Oracle - esp reporting tools, BI, warehousing, and everything had bindings for relational databases.
Not sure how that translates as a business model, as no one owns git (like Oracle owned oracle). However, although Sun didn't make money from java, everyone else did - so there is a business model, just as a user of git, not an owner. e.g. reporting tools based on git; CI tools, code quality tools.
So maybe the answer is to just to treat git as infrastructure, for the app you sell, as opposed to trying to make money from the infrastructure itself. Linux is a similar product.
Not sure how that translates as a business model, as no one owns git (like Oracle owned oracle). However, although Sun didn't make money from java, everyone else did - so there is a business model, just as a user of git, not an owner. e.g. reporting tools based on git; CI tools, code quality tools.
So maybe the answer is to just to treat git as infrastructure, for the app you sell, as opposed to trying to make money from the infrastructure itself. Linux is a similar product.