It makes use of eclipse jetty.
You can validate it by digging on project's source code and especially jackrabbit-standalone module.
Snippet from pom.xml of aforesaid module:
...
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<extensions>true</extensions>
<configuration>
<instructions>
<Export-Package>
org.apache.jackrabbit.standalone
</Export-Package>
<Embed-Dependency>
*;inline=*.txt|*.html|*.jsp|*.xml|*.jar|*.properties|remoting/**|bootstrap/**|javax/**|repackage/**|images/**|com/**|ch/**|jline/**|Resources/**|css/**|schema*/**|EDU/**|error/**|org/**|META-INF/*.tld|META-INF/maven/**|META-INF/services/**|WEB-INF/config.xml|WEB-INF/*.properties|WEB-INF/templates/**
</Embed-Dependency>
<Embed-Transitive>true</Embed-Transitive>
<Main-Class>org.apache.jackrabbit.standalone.Main</Main-Class> <- This is the main class of the jar
</instructions>
</configuration>
...
Snippet from org.apache.jackrabbit.standalone.Main:
...
import org.eclipse.jetty.server.Server;
...
private final Server server = new Server();
...
server.start();
...