Spent most of today trying to get CDE (opencde, actually) to run on Ubuntu, it ain't easy. Still haven't succeeded. I came across this, for when you are trying to compile something and the son of a bitch keeps giving you missing header file errors.
$ sudo apt-get install apt-file
$ sudo apt-file update
$ apt-file search Xm/Xm.h
It will then list the packages which contain the missing file. Hell, how come I only found out about this now?
griffin@desker:~$ apt-file search Xm/Xm.h
libmotif-dev: /usr/include/Xm/Xm.h <-- look, there's the sonofabitch right there!
Installed libmotif-dev and I eventually got the sucker to compile. Since documentation is zero, I still haven't gotten the thing running yet. Ubuntu does not use xinitrc or anything, so changing desktop manager is a pain. I'm still not sure which opencde binary I should be using anyway, but I've had enough for today.