BRMS platform 5.2 contains the follow components:
EWP 5.1.1
Modeshape 2.5.1.GA
Drools 5.2.1.BRMS

There are mainly 3 ways to build BRMS-P
1) Local build.  
2) Hudson build, see: https://hudson.qa.jboss.com/hudson/view/BRMS-P-Release-Build/
3) MEAD build.(See MEAD build command example: The milestone build are supposed to build via MEAD for BRMS 5.2, search the build via https://brewweb.devel.redhat.com/

Here are some notes for local build. 
You need maven 3.0.3 or above and jdk 1.6.0_24 to proceed BRMS-P build
The easiest way to build  brms-p locally is to obtain all the dependencies from MEAD repo which is highly recommended.

1)To create a settings file named ~/.m2/mead-settings.xml with the following contents:
    <settings>
      <mirrors>
        <mirror>
          <id>MEAD repository</id>
          <mirrorOf>*</mirrorOf>
          <url>http://download.devel.redhat.com/brewroot/repos/soa-brms-5.2-build/latest/maven</url>
        </mirror>
      </mirrors>
    </settings>
    Then run:
2)mvn -s ~/.m2/mead-settings.xml clean install

To check that all required dependencies are actually in the MEAD repository run:
mvn -s ~/.m2/mead-settings.xml -Dmaven.repo.local=/tmp/m2-mead -DaltDeploymentRepository=koji-repo::default::file:///tmp/repo-mead clean deploy

Well, if you are unable to access MEAD repo or there is another reason you want all brms-p dependency by yourself. Then I hope the following would help.
1) Build modeshape
  git clone git://git.app.eng.bos.redhat.com/Modeshape/modeshape.git modeshape
  cd modeshape && mvn -Passembly -DskipTests clean install 
  
2) Build Drools modules
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-build-bootstrap.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-knowledge.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/drools.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/jbpm.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/guvnor.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-tools.git
  git clone git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-integration.git

  cd droolsjbpm-build-bootstrap && mvn -Dfull -Dsoa  -DskipTests clean install
  cd droolsjbpm-knowledge && mvn -Dfull -DskipTests clean install
  cd drools && mvn -Dfull -Dsoa -DskipTests clean install
  cd jbpm && mvn -Dfull -Dsoa -DskipTests clean install
  cd guvnor && mvn -Dfull -Dsoa -DskipTests clean install
  cd droolsjbpm-tools && mvn -Dsoa -DskipTests clean install 
  cd droolsjbpm-integration && mvn -Dfull -DskipTests clean install

3) Build brms-p
  mvn -Pfetch.external clean install


Here is a reference of MEAD build command(Please make sure to replace the code version you actually want to build) :
brew maven-build soa-brms-5.2-candidate git://git.app.eng.bos.redhat.com/Modeshape/modeshape.git#24938f14255fdc2a037ae6f4ac45e57d3e231fb6 -Passembly -DskipTests=true
brew maven-build soa-brms-5.2-candidate -Dfull=true -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-build-bootstrap.git#3374a1c1690dd5bafb72dc3d31c93bcc7f83e0a1
brew maven-build soa-brms-5.2-candidate -Dfull=true -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-knowledge.git#b5d80275a132e52dec2ec6707e1e1bc87decf545
brew maven-build soa-brms-5.2-candidate --scratch -Dfull=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/jbpm.git#4f053c6d8287968159ae21694f57e81607c49d51

brew maven-build soa-brms-5.2-candidate --scratch -Dfull=true -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/guvnor.git#21e25d19adbfc259d6c55ce6bf0288ab415ea9f9
brew maven-build soa-brms-5.2-candidate --scratch -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-tools#02e0deed007be7745a42ed97f29653d4b91d0cef


brew maven-build soa-brms-5.2-candidate -Dfull=true -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/droolsjbpm-integration.git#89ecbc7e75b1eabc8ff29fce8916c2d632866ebd

brew maven-build soa-brms-5.2-candidate -Dfull=true -Dsoa=true -DskipTests=true git://git.app.eng.bos.redhat.com/droolsjbpm/drools.git#641fb987c6c567c4182711f4ca63b43be0cdf54e

brew maven-build soa-brms-5.2-candidate svn+http://svn.devel.redhat.com/repos?jboss-soa?/trunk/brms-p#9635 

