Does JAX-RS needs a war module?

From the JAX-RS Specification 2.0 p. 8:

2.3.2 Servlet

A JAX-RS application is packaged as a Web application in a .war file. The application classes are packaged in WEB-INF/classes or WEB-INF/lib and required libraries are packaged in WEB-INF/lib. See the Servlet specification for full details on packaging of web applications.

This is the standard way if you want to deploy your JAX-RS application in a web-container. However the specification points also out that applications can run in different containers like ejb-containers or even an Java SE environment. But for other containers there is nothing specified:

An implementation MAY provide facilities to host a JAX-RS application in other types of container, such facilities are outside the scope of this specification.