Thanks for sharing. Was there able to be any code sharing between the Motif/OpenLook versions and the DOS/OS/2 versions? (Or just concepts?)
The other thing I should've mentioned is that at the time, OS/2 did look like the surer bet than Windows. The success of Windows surprised everybody (including, I think, Microsoft.)
The spreadsheet engine was a port of the DOS version, which by that time was written in C. The GUI ran as a separate process and communicated with the engine via a character protocol into a bastardised "terminal driver".
This fabulous kludge was driven by the testing regime: if we changed one byte of the spreadsheet engine it would trigger person-years of manual testing.
Indeed the OS/2 2.0 debacle is one of the worst debacles in MS's history.
Technical issues aside, Windows by itself made MS >$100B over the last 10 years. If that's 'one of the worst debacles'...
(I did like MS OS/2 2.0 though...)
Their solution was to go multi-platform, with an all-singing cross-platform super-product that would run everywhere. Except it didn't actually run anywhere; it broke under its own weight.
So they were very much behind when they finally buckled down to porting the 1-2-3 codebase to Windows in 1991.
Source: I was on the team that shipped the Motif and OpenLook versions of 1-2-3, separate but concurrent to the above.