I would argue that the fact that Arrow has been integrated into so many projects over the last year is proof that a separate project made sense. Dremio, PySpark, Pandas, MapD, NVIDIA GPU Data Frame, Graphistry, Turbodbc, ...
Well... use in projects is an indicator, not a proof, of utility. Not all choices are good ones, inferior & redundant products are crop up on a regular basis, and to the dismay of many in this community, sometimes win out. Happily, from the article, Arrow, doesn't appear one of them, and has its own unique and justified niche.
We considered starting a company in SF a couple years ago. I'm glad that we decided to instead start it in Mountain View (http://www.dremio.com). We're able to attract very talented people from San Jose, Milpitas, Redwood City, etc. where rents are a bit more reasonable.
Unless there's a really good reason to not split it equal, I think it's better if both founders have the same amount of equity. Otherwise you could create unnecessary tension which is the last thing you want at that early stage.
Another analogy that might help is strongly typed vs. loosely typed languages. There are pros and cons to both Java and Python, and both are widely used.
I think there's a tradeoff here. It's like MongoDB - hundreds of thousands downloads per month because it enables people to build and deploy applications faster. For many cases a relational database is still better though.
The nice attribute of Drill is that it works on schema-less data as well as data with strong schemas. The user can make the tradeoff between agility and 'safety'.
