Hi Bruno,
This is a bit odd, Snowdrop 2 should have no issues with JBoss AS 6 - there is a change in package names between JBoss 5 and JBoss 6, but Snowdrop 2 is aware of it (and using VFS3).
Are you sure that you use this dependencies?
<dependency>
<groupId>org.jboss.snowdrop</groupId>
<artifactId>snowdrop-deployers</artifactId>
<version>2.0.0-M1</version>
</dependency>
<dependency>
<groupId>org.jboss.snowdrop</groupId>
<artifactId>snowdrop-vfs</artifactId>
<version>2.0.0-M1</version>
</dependency>
However, I am under the impression that you are affected by https://jira.springsource.org/browse/SPR-7197. If you use Spring 3.0.3 or later, you may be running your WAR with Spring only (no Snowdrop).