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):
>It seems that commits prior to 6a7a141 were covered under the MIT license. It's unclear why it was deleted (the commit message is only "Delete").
Not currently free software / open source for some reason, no LICENSE file at the moment. For those who were also wondering.