unfortunately the old Blender 2.49b has still some import/export functions that newer versions of blender do not have. So I used this program always besides the newest version of Blender. In the past (until Ubuntu 12.04, 64bit) I had no problem to install old Python 2.6 and than Blender 2.49 worked. Since I work on Ubuntu 16.04 (64bit) I am not able to use old Blender 2.49. Is there any solution?
I can think of three options -
Compile blender yourself or find someone that maintains an old version of blender for recent systems. Old versions fail to work as they were compiled against old library versions that are no longer available, some small patching will most likely need to be done.
Setup an old system to run blender 2.49. You can install a second system to boot from or create a virtual setup using Xen or Qemu... this will allow you to have the old system that can still run 2.49 when you need to use it.
Create an import addon for the current version of blender. Blender's python API was completely changed in 2.50 so any old scripts from 2.49 will need to be re-written for the current version. You can get blender specific scripting help at blender.stackexchange.com, if you start by asking for help importing a file format you might get someone pointing you to an addon that has already been made or offering to help you start a new addon.