Try not to read too much into that, the MIT license was in the original blank repo I started with. There are a few questions I need to get answered, so the lack of that file doesn't necessarily mean anything about the license. The previous Descent 1&2 releases were under the license seen here, I would expect that at minimum (minimum permissibility-wise):

https://github.com/OpenSourcedGames/Descent-2

I'm hoping the owners will be able to agree to MIT, but we're doing due diligence right now.