what is their incentive for doing this, i doubt its out of altruism or "giving back"
I think the goal is efficiency. The realization that having a shared data strategy across the industry benefits everyone, including regulators, and make technology stacks more efficient.
Of course, like any other tech company, I think there's the desire to mutualize the cost of maintaining a core component (e.g. Facebook with Cassandra, Google with Kubernetes, etc).
And I mean, it got open sourced 2 days ago...so 100 stars is not that I bad I think...
And the trend is pretty positive https://porter.io/github.com/finos/legend
Would love to hear your feedback