License hinders our integrability

[adam2392]

I am revisiting the license issue, which I think will hinder a lot of involvement from OSS community + hinder any ability to integrate with scikit-learn and EconML.

I am actually now unsure why we changed the license because JHU doesn't own this software to my knowledge, and they can't make money off of it anyways?... I propose a two-step procedure:

1. Change license to MIT to match PyWhy: https://github.com/py-why/EconML/blob/main/LICENSE
2. Potentially revisit integrating into scikit-learn-contrib to get a larger involvement in OSS community. Would be good for visibility to get the repo within an org that has more visibility, or branding for treeple.

cc: @SUKI-O I saw you were the last commit for license?