We have a bunch of *nix machines some of which probably have IBM software installed on them.
Is there a way to identify the machines and the type of IBM software that is installed?
If you have used package managers of different *nix to install software, you can list and classify them using that.
for eg: lslpp (-l or -L) will list packages in an IBM AIX box. pkginfo will do that in SUN Solaris rpm -qa will list the packages in RHEL
Now if you used pre-compiled versions or installed from source by compiling the package by hand, they will be left out by the above approach. The only way, I can propose to detect and classify them (if any) is the painful route of looking at the running processes and open ports, then use that to correlate back to a package. Then from such packages identify IBM software. This is surely will not an easy process :(
Listing package names and/or running processes as Jamess indicates is a good way to start. But what is your goal exactly? Do you need to have an installed IBM software overview, or do you need to calculate how many software licenses you require? And are there specific IBM products you are expecting to find? I create IBM installation overviews on a daily basis - email me at kdingjan at solarcom-consulting dot com in case you need detailed help.