GWT Mosaic Could not find an exact match rule...e

I'm using the gwt-mosaic 0.4.0-rc4. I have the following errors after a mvn gwt:compile :

[INFO] --- gwt-maven-plugin:2.3.0-1:compile (default) @ ... ---
[INFO] auto discovered modules [...]
[WARNING] Don't declare gwt-dev as a project dependency. This may introduce complex dependency conflicts
[INFO] Compiling module ...
[INFO]    Validating newly compiled units
[INFO]       [WARN] Warnings in 'jar:file:/home/seyz/.m2/repository/com/googlecode/gwtmosaic/gwt-mosaic/0.4.0-rc4/gwt-mosaic-0.4.0-rc4.jar!/org/gwt/mosaic/ui/client/impl/GlassPanelImpl.java'
[INFO]          [WARN] Line 52: Referencing deprecated class 'com.google.gwt.user.client.impl.DocumentRootImpl'
[INFO]          [WARN] Line 60: Referencing deprecated class 'com.google.gwt.user.client.impl.DocumentRootImpl'
[INFO]    Scanning for additional dependencies: jar:file:/home/seyz/.m2/repository/com/googlecode/gwtmosaic/gwt-mosaic/0.4.0-rc4/gwt-mosaic-0.4.0-rc4.jar!/org/gwt/mosaic/core/client/DOM.java
[INFO]       Computing all possible rebind results for 'org.gwt.mosaic.core.client.impl.DOMImpl'
[INFO]          Rebinding org.gwt.mosaic.core.client.impl.DOMImpl开发者_运维百科
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.core.client.impl.DOMImplIE8'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]          Rebinding org.gwt.mosaic.core.client.impl.DOMImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.core.client.impl.DOMImplIE8'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]    Scanning for additional dependencies: jar:file:/home/seyz/.m2/repository/com/googlecode/gwtmosaic/gwt-mosaic/0.4.0-rc4/gwt-mosaic-0.4.0-rc4.jar!/org/gwt/mosaic/core/client/UserAgent.java
[INFO]       Computing all possible rebind results for 'org.gwt.mosaic.core.client.impl.UserAgentImpl'
[INFO]          Rebinding org.gwt.mosaic.core.client.impl.UserAgentImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.core.client.impl.UserAgentImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]          Rebinding org.gwt.mosaic.core.client.impl.UserAgentImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.core.client.impl.UserAgentImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]    Scanning for additional dependencies: jar:file:/home/seyz/.m2/repository/com/googlecode/gwtmosaic/gwt-dnd/0.4.0-rc4/gwt-dnd-0.4.0-rc4.jar!/com/allen_sauer/gwt/dnd/client/util/DOMUtil.java
[INFO]       Computing all possible rebind results for 'com.allen_sauer.gwt.dnd.client.util.impl.DOMUtilImpl'
[INFO]          Rebinding com.allen_sauer.gwt.dnd.client.util.impl.DOMUtilImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='com.allen_sauer.gwt.dnd.client.util.impl.DOMUtilImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]          Rebinding com.allen_sauer.gwt.dnd.client.util.impl.DOMUtilImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='com.allen_sauer.gwt.dnd.client.util.impl.DOMUtilImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]    Scanning for additional dependencies: jar:file:/home/seyz/.m2/repository/com/googlecode/gwtmosaic/gwt-mosaic/0.4.0-rc4/gwt-mosaic-0.4.0-rc4.jar!/org/gwt/mosaic/ui/client/GlassPanel.java
[INFO]       Computing all possible rebind results for 'org.gwt.mosaic.ui.client.impl.GlassPanelImpl'
[INFO]          Rebinding org.gwt.mosaic.ui.client.impl.GlassPanelImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.ui.client.impl.GlassPanelImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]          Rebinding org.gwt.mosaic.ui.client.impl.GlassPanelImpl
[INFO]             Could not find an exact match rule. Using 'closest' rule <replace-with class='org.gwt.mosaic.ui.client.impl.GlassPanelImplIE6'/> based on fall back values. You may need to implement a specific binding in case the fall back behavior does not replace the missing binding
[INFO]    Compiling 12 permutations
...

Do you know what these errors mean ?

These are all warnings, not errors. The first one, printed twice states merely that the class being referenced is deprecated in the latest gwt version, and may not exist in future versions, so the library should remove its use of it.

All of the other messages indicate that IE9 support has been added, and that your library has no IE9 support. As such, the compiler is building an IE9 build using another version of IE code.