Pre-built ready to use osu!auto+ is linked in the description of this YouTube video.
This project contains osu!auto+ patches to the 2016 leaked osu! source code. To apply them, make sure you're in a git repository with the clean osu! code and run git am --keep-cr path/to/this/repo/*.patch, where path/to/this/repo/ is the path to the folder with .patch files from this repository.
After building the client (I used either the Debug or the PublicNoUpdate configuration), make sure to put Spline.dll into the resulting osu! folder.
osu!auto+ is a rewrite of the built-in Auto mod which attempts to obtain the highest possible scores on 2B maps, which the standard Auto does really poorly on. Additionally, osu!auto+ includes somewhat customizable cursor dancing and cursor trail tweaks. You can watch it in action in this YouTube playlist.
The Spline folder contains the source code for Spline.dll. It's separated out because when I was adding spline interpolation I had this homework assignment with some necessary linear algebra laying around, so I just re-used the code. Thus the code quality is probably sub-ideal. Sorry for inconvenience.