Sorry time progresses and backward compatibility isn't possible. Python has moved on and the Python developers have opted for new feature over compatiblity. The Poser developers had no option but to accept the only version currently supported. We have to live with choices made by others.

The problem isn't as big as it seems. Anything available in uncompiled format can be used (with some small modifications in a few cases). Most compiled scripts are now available in a new version and most are a free upgrade. Unsupported scripts probably require some rethinking as most things can be done in a better nowadays.