From https://forum.zdoom.org/viewtopic.php?p=1264012
Chris wrote: Officially, the OpenAL DLL on Windows is OpenAL32.dll (even for 64-bit, oddly). That's what apps are supposed to link to and use. The original redistributable given by Creative Labs provided an OpenAL32.dll that was a "router"; it would look for other *oal.dll "driver" files supporting the OpenAL API and expose their respective devices to apps as a single collective (wrap_oal.dll which is the "wrapper driver" that could either use DirectSound3D or a software mixer, and ct_oal.dll is a hardware driver that directly uses Creative devices, for example; soft_oal.dll is how OpenAL Soft can be added to that set as another driver).
Since each of these drivers is itself just an OpenAL implementation, any one can be named OpenAL32.dll and used directly without the router. There's also nothing stopping an app from loading soft_oal.dll or whatever without renaming it, if it wants. (G/U)ZDoom only officially supports OpenAL Soft (others may work, but can be missing key functionality or run into bugs), and has historically provided an OpenAL32.dll that's OpenAL Soft. I guess UZDoom changed this to load soft_oal.dll instead, but either way is functionally the same.