Downloading Atmosphere's SNAPSHOT - Atmosphere/atmosphere GitHub Wiki
To download Atmosphere SNAPSHOT version, just add in your Maven's ~/.m2/settings.xml:
<repositories>
<repository>
<id>oss.sonatype.org-snapshot</id>
<url>http://oss.sonatype.org/content/repositories/snapshots</url>
</repository>
</repositories>
Or manually download them