Hello,
these lines from your server.log are important:
10:52:29,234 INFO [org.jboss.as.controller] (Controller Boot Thread) Service status report
New missing/unsatisfied dependencies:
service jboss.jdbc-driver.mysql (missing)
10:52:29,250 ERROR [org.jboss.as] (Controller Boot Thread) JBoss AS 7.0.2.Final "Arc" started (with errors) in 11766ms - Started 95 of 153 services (3 services failed or missing
You have badly configured your MySQL driver. This is not a jBPM problem, You can find steps for setting up a DB driver on many places, for example in JBoss AS 7 documentation.