bz2.dll, what is it for?

[Blue Shadow]

There's a file which is called bz2.dll bundled with GZDoom 4.14.1. What is it for? Checking the details pane in the file's properties yields nothing. There's no information whatsoever.

Something else I notice, which is unrelated to the above, is the lack of the license.zip in GZDoom 4.14.1.

[Graf Zahl]

This is the DLL version of the bzip2 decompression library. I have no idea why it needed to be included in DLL form, it's presumably some screwed up setup that made CMake select this over the internal version.