Among the many UI accomplishments by Keith Ohlfs at NeXT is this wonderful little font. It has never been modernized to work on the current version of the OS and unfortunately Keith passed away unexpectedly (October 26th, 2016). Anyone who is willing to help in this effort is invited to join.
Original sources from NeXTStep /Library/Fonts are in Ohlfs.font/.
BDF files from which Ohlfs.font/Ohlfs.bepf is generated are archived in github.com/johnsonjh/NeXTDPS.
Updated BDF files (see Process) are in Updated_BDFs/.
Ohlfs-Light.otf is based on the updated bitmaps for 9, 10, 12, and 14px; it includes a vector description and embedded bitmaps
Ohlfs-Medium.otf is based on the updated bitmaps for 16 and 18px; it also includes a vector description and embedded bitmaps
Ohlfs.dfont and Ohlfs.ttf are based on the original (non-updated) BDF files
The files in Updated_BDFs/ were amended to include lines explicitly describing pixel_size, point_size, and resolution. This makes them interpretable by FontForge, from which SFD-format bitmaps were generated. These SFDs were fed through BitsNPicas to generate vector fonts. FontForge was then used again to combine those vectored fonts with their bitmap strikes.
Since the bitmap strikes for 9-14px and 16-18px are substantially different, they are presented here as different weights of the Ohlfs font family.