Did the OS/2 source get transferred with the OO source and if so where is it?
(To be clear with OS/2 code I mean stuff/adaptions necessary to build the software to run on OS/2, not the code of the operating system itself, but I guess you meant the same)
While the existing code that was in the OOo-repositories at the time of the split has been transferred, there has not been a maintainer for the OS/2 port on the LibreOffice side (and there have never been official releases of OpenOffice.org either).
So without people creating builds for OS/2, and with all the changes in the build infrastructure (move to gnu make), all the code changes and refactoring, chances are that it won’t build out-of-the box and will need some love to get running again.
So the bottom line is: No OS/2 maintainer in sight, so no build of LibreOffice for OS/2. If someone is willing to work on the port, that person of course is very welcome.
The only maintainer of OS/2 port for OOo has shown up over at Apache, so it is unlikely that he will also create LibreOffice builds.