I run pbterm on the e-reader. the "shell" command : /mnt/ext1/system/bin/pbimageviewer.app
the answer is :
$ /mnt/ext1/system/bin/pbimageviewer.app
/bin/ash: /mnt/ext1/system/bin/pbimageviewer.app : not found
maybe I will try with the firmware update to 5.X... but i read it's beter to be in 4.X
I try too with /mnt/ext1/applications/pbimageviewer.app
but it did not found it. the app. is visible on the e-reader.