The error is:

Your original request has been modified.
"JBoss Tools Java Standard Tools Tern.java Adapter" is already installed, so an update will be performed instead.
Cannot complete the install because of a conflicting dependency.
Software being installed: JBoss Tools Java Standard Tools Tern.java Adapter 3.7.0.Alpha2-v20150417-0104-B13 (org.jboss.tools.jst.jsdt.feature.feature.group 3.7.0.Alpha2-v20150417-0104-B13)
Software currently installed: JBoss Developer Studio (Branded Product) 9.0.0.Alpha2-v20150405-1144-B2918 (com.jboss.devstudio.core.package 9.0.0.Alpha2-v20150405-1144-B2918)
Only one of the following can be installed at once:
JBoss Tools Java Standard Tools - Tern Project Adapter 3.7.0.Alpha2-v20150322-0547-B822 (org.jboss.tools.jst.jsdt 3.7.0.Alpha2-v20150322-0547-B822)
JBoss Tools Java Standard Tools - Tern Project Adapter 3.7.0.Alpha2-v20150417-0104-B13 (org.jboss.tools.jst.jsdt 3.7.0.Alpha2-v20150417-0104-B13)
Cannot satisfy dependency:
From: JBoss Developer Studio (Core Features) 9.0.0.Alpha2-v20150405-1144-B2918 (com.jboss.devstudio.core.feature.feature.group 9.0.0.Alpha2-v20150405-1144-B2918)
To: org.jboss.tools.jst.jsdt.feature.feature.group [3.7.0.Alpha2-v20150322-0547-B822]
Cannot satisfy dependency:
From: JBoss Developer Studio (Branded Product) 9.0.0.Alpha2-v20150405-1144-B2918 (com.jboss.devstudio.core.package 9.0.0.Alpha2-v20150405-1144-B2918)
To: com.jboss.devstudio.core.feature.feature.group [9.0.0.Alpha2-v20150405-1144-B2918]
Cannot satisfy dependency:
From: JBoss Tools Java Standard Tools Tern.java Adapter 3.7.0.Alpha2-v20150322-0547-B822 (org.jboss.tools.jst.jsdt.feature.feature.group 3.7.0.Alpha2-v20150322-0547-B822)
To: org.jboss.tools.jst.jsdt [3.7.0.Alpha2-v20150322-0547-B822]
Cannot satisfy dependency:
From: JBoss Tools Java Standard Tools Tern.java Adapter 3.7.0.Alpha2-v20150417-0104-B13 (org.jboss.tools.jst.jsdt.feature.feature.group 3.7.0.Alpha2-v20150417-0104-B13)
To: org.jboss.tools.jst.jsdt [3.7.0.Alpha2-v20150417-0104-B13]