Here are some screenshots of it, including InterfaceBuilder http://www.shawcomputing.net/resources/apple/os_pictures/yb2...
According to https://www.betaarchive.com/forum/viewtopic.php?t=29049 there's an even older version branded “OPENSTEP Enterprise 4.2 for Windows” instead of Yellow Box.
edit: Neat, I never realized TextEdit was a Java Yellow Box app. Cool way to both test/dogfood and market the Java bindings: http://www.shawcomputing.net/resources/apple/os_pictures/yb2...
Also, it's not-even-mildly interesting but the Start Menu shortcuts are oppositely-spaced compared to the branding within the apps themselves for some reason — i.e. “Project Builder” vs “ProjectBuilder” and "YellowBox” vs “Yellow Box”. And it comes with a Bourne Shell! http://www.shawcomputing.net/resources/apple/os_pictures/yb2...
IIRC OPENSTEP Enterprise for Windows was a version before Rhapsody and was actually an official release. I had this on CD-ROM, I might actually still have it somewhere.
There was also a OPENSTEP Solaris for Sparc, but I think this was a bit more obscure, don’t have any firsthand experience with that.
https://www.flickr.com/photos/96579068@N05/13061732584/
I was working for a bank around that time and we used a trading system which was initially running on NeXT boxes, but we had it also running on NT 4.0 later on.
Edit: I think I even found some screenshots of that trading application:
https://th.bing.com/th/id/R.8d154655f6713bc112d178164e4ffe51...
This seems to be running on Windows XP, so that was quite a bit later. But if you look at the toolbar icons, the heritage is quite clear ;)
