Dealing with technical debt while maintaining compatibility can be a developer nightmare. turning a program started when cpu had one core, 16 bits  and so few Ghz  to the massively parallel nowadays architectures is challenging too. Covering the code with unit tests is mandatory before refactoring seriously, but it cannot be seen by users.
I don't think it's dead. But the team cannot get open source code taken from other projects in it only.The last release came with this intriguing sentence :

This release marks a change of direction for the Poser development team.  Customers can expect ongoing updates to Poser 13 for the next 12-24 months as the team explores new technologies for the next major version of Poser.

so i believe they gave up and try to start something else, we just can try to  guess what : Transform poser into a paying Blender plugin for posing ?