How to build maven project without version?

You will always need a version number for a project, however it is possible to change the name of the generated package (JAR, WAR, EAR, etc.) through the <finalName> element in the POM.

<project>
    ...
    <build>
        ...
        <finalName>${project.artifactId}</finalName>
        ...
    </build>
    ...
</project>

or in older versions of maven:

        ...
        <finalName>${artifactId}</finalName>
        ...

By default, the finalName is ${project.artifactId}-${project.version}, but this can be changed to something else. This will only affect the name of the package created in the target directory; the file name in the local repository and uploaded to remote repositories will always have a version number.

See the POM reference documentation for more information.