What is the difference between the 2 because both of them are based on the same methodology of publishers and subscribers who exchange messages between them via topics/subjects?
JMS is a Java-based API for asynchronous messaging supporting both point-to-point and pub-sub semantics. It can be implemented by anyone. Apache ActiveMQ is probably the most popular and well-known JMS implementation, although there are numerous implementations.
AMPS is a proprietary messaging system developed by 60East Technologies which appears to only support pub-sub semantics.