JCR
A specification for hierarchical repositories.
ModeShape
JBoss JCR implementation used by Fedora 4.
XACML
XML language to specify authentication policies.
Sonar
A source code metrics reporting tool.
Jenkins
A continuous-integration tool.
Jetty
A light-weight server.
Infinispan
The data grid used by Modeshape for storage and clustering.
LevelDB
The default key-value store used by Fedora 4.
JGroups
Clustering technology.
Spring
A dependency-injection framework (a container that wants to manage everything, in practice).