Correct, by default JRules comes with Studio and RES.
RES is a WAR file you need to deploy on a WAS. I think that by default it is only provided with the messy WebSphere but you can download some "bundles" for JBoss, WebLogic, ... and more.
Program / Ilog Jrules / documentation / How to install RES - RTFM
One could use WebSphereCE but this is just crappy.
It is provided by default and you can use that straight away but you don't want to use it in live or even for POCs.
We call this pseudo WAS "Bernardo" like in Zorro because it is silent :)
BTW: you don't need RES to execute a rule. Specially with JUnit, you can export the ruleapp or ruleset (I don't remember) and use POJO straight away.
Create a new project in Studio called: "new java project for rules" ish and the wizard will create all you need to execute your rules locally.
You will just need to code the InputParameters and retrieve the OutputParameters in order to assert.
EZ PZ lemon squizzy :)
From there you can load the ruleapp in your "before" JUnit method, makes sense?
Rather that connect the RES itself.
To sum up, if I were you:
1/ I would create the example project I mentioned. So I have the code example.
2/ I create my own ruleapp (right click on the rule project / export / ruleapp) and store it somewhere.
3/ prepare my JUnit classes - Assertion + "Before" methods
4/ run it locally without RES
5/ I'm happy as Larry
6/ Now I deal with RES and configure it
Hope it helps