Oracle Weblogic Server is described as 'Oracle WebLogic Server 12c is the #1 application server across conventional and cloud environments, providing extreme cloud performance, scalability, and elasticity'. There are four alternatives to Oracle Weblogic Server for Linux, Windows, Mac, Java and Java Mobile. The best alternative is JBoss, which is both free and Open Source. Other great apps like Oracle Weblogic Server are WebSphere Application Server (Paid), Apache Geronimo (Free, Open Source) and Payara Server (Free, Open Source).
JBoss is Red Hats Java EE 5-compliant (soon Java EE 6-compliant) application server. It is, as with Red Hat itself, dual-licensed either as open source (community edition) or commercially (enterprise edition).