it's not possible to start Crowd from outside the Crowd install directory

(12:06) (c:0j:0)[nowaker@$nwkr-sp:~]% ~/opt/crowd-2.2.7/inst/start_crowd.sh  exec: 2: apache-tomcat/bin/startup.sh: not found 

You should never make any assumptions on what the current working directory is. It's a common pattern that you first cd "`dirname "$0"`" in any script that needs to execute another scripts in its install directory.