As explained in Appendix A of [RefModel] a Transaction Manager can be though as a subset of a Transaction Monitor. Most commercial products tend to merge the features in a single bundle; this is good if you need a Transaction Monitor, this may be bad if you only need a Transaction Manager.
IBM TXSeries[3] is a Transaction Monitor with an integrated Transaction Manager. Oracle (BEA) Tuxedo[4] is a Transaction Monitor with an integrated Transaction Manager. JBoss[5] is a JEE (Java Enterprise Edition) application server; it is a Transaction Monitor with an integrated Transaction Manager for Java based applications.
JOTM (Java Open Transaction Manager) and BTM (Bitronix JTA Transaction Manager) are Transaction Managers, but they are not Transaction Monitors and they can be used in conjunction with a JVM (Java Virtual Machine) and possibly any Transaction Monitor. Unfortunately they are Java based technologies and not native ones; in the Java arena there are a few stand-alone Transaction Manager, while in the C language arena it is not easy to find out one.
The LIXA project implements a distributed Transaction Manager that your Application Programs can use to coordinate a distributed transaction among two or more Application Programs running on different systems.
XTA has been designed to support polyglot use cases in distributed environments and it can potentially support many programming languages. See Chapter 8, Developing Application Programs using XTA (XA Transaction API) interface for more information about XTA.
The LIXA project implements a stand-alone Transaction Manager that your Application Program can use in many different ways:
from a C application launched from shell or something else
from a COBOL application launched from shell or something else
With the aid of the LIXA Transaction Manager potentially any web server can be converted in an Application Server with two phase commit support.