I remember that I wrote my first Enterprice Java Application about 10 years ago, when the first EJB(1.0)specification back then was not fully developed.  That applaction used the Weblogic application server.  It was quite complicated to deploy the EJB to the server.  I wrote the EJB codes, remote, home interface, the bean it.  I also wrote the descriptor.   Using Java EE's utilities to compile the bean and generate the stub, etc.  I then converted the application to EBJ2.0 when EBJ2.0 became available.  It converted it and tried in on Weblogic server 8.x and Sun's Application 8.x.  The application worked on both servers.  It was easier to work with EBJ2.0. 

Reference:

http://today.java.net/pub/a/today/2007/01.23/migrating-from-ejb2x-to-ejb30.html