Apart from the already mentioned OPENSTEP for Enterprise, see also here: https://www.stone.com/dev/StonesThrow2/OneFoxTwoFox.html https://www.stone.com/dev/Sto

Apart from the already mentioned OPENSTEP for Enterprise, see also here: https://www.stone.com/dev/StonesThrow2/OneFoxTwoFox.html https://www.stone.com/dev/StonesThrow2/OneFoxTwoFox.html Basically, it was called Yellowbox, but it didn’t officially survive the release of Mac OS X IIRC. But Apple was at least still using parts of it for some Windows ports back then I believe.