This is false.
The latest JMS 1.3.x works on all Joomla 2.5 and 3.x version.
This person purchased the old JMS 1.2.x that is working on Joomla 1.5 till 2.5.9 and a red warning message clearly show that.
This red message exists for april 2013 when joomla 2.5.10 changed the functionality of the Joomla installer and introduced a regression bug that make joomla installer incompatible with older installer.
We reported this regression bug into the joomla bug tracker 30206 and we can just hope that joomla will fix this change of functionality to be compatible with older installer.
The solution is to rollback the joomla installer and discard the change of functionality present in J2.5.10 that is a result of a change request from RedComponent for their Red Shop extension version 2
This person never contact us and never replied to our email but complain at paypal to which we have replied and now in joomla where you can read this reply