I am following the steps for installation and configuration of commerce reference store onThe documentation which you seem to be referring is for ATG/CRS10.1 which does support evaluation install with Weblogic. However, since you are on ATG/CRS10.0.3 so you should refer to following docs where you will find only JBoss mentioned in the evaluation installation requirements:
I have installed ATG10.0.3 and CommerceReferenceStore10.0.3.2.
The Question that Do I need to install JBoss and reinstall ATG Commerce to point to JBoss installation instead of pointing to Weblogic as was done in my case.In case you do want to go with evaluation install only then you can install JBoss and then update your existing ATG installation to point it to use JBoss. For that you can update dasEnv.bat file present in <ATG>\home\localconfig by commenting the Weblogic specific environment variables and setting the JBOSS_HOME & JBOSS_VERSION environment variables like: