The newer Appache was compiled with gcc 3.2 and newer libraries. I would suspect that you'd have to fully upgrade your libraries and compiler to get many Slackware 9 packages to run in Slackware 8.1. You may as well upgrade the whole thing in that case. On the other hand, I found that most of my binaries from Slackware 8.1 and even 8.0 still run in Slackware 9.0. There have been a few exceptions to this. IMHO, if you are planning to upgrade a program, but do not wish to upgrade the OS, compile from source.
