Modeller has a few prerequisites which should generally be satisfied on modern operating systems. If, however, you have a very old operating system, workarounds are detailed on this page.
Modeller requires the glib library version 2.2 or later, but RedHat 8.0 ships with glib 2.0. (When trying to run Modeller, you will see an error like the following: mod9v2_i386-intel8: relocation error: libmodeller.so.1: undefined symbol: g_vsprintf)
For a simple workaround, you can copy the glib library from RedHat 9 into your Modeller installation. For example, for 32-bit RedHat 8.0, just get /usr/lib/libglib-2.0.so.0 from a RedHat 9 system (can also be downloaded from our website) and put it in the lib/i386-intel8 directory under your Modeller installation. (If you installed from RPM, this will be /usr/lib/modeller9v2/lib/i386-intel8/ or similar.) To install the RPM in the first place, add the --nodeps option (otherwise it will complain that it needs glib2 >= 2.2).