I have tried to follow the same path, but failed to make it work.

Then tried to follow a different approach. 

initially started with :

sudo mkdir -p /Users/adnan/rubydev/openproject/{pgdata,logs,static}

docker run -d -p 8090:80 --name openproject -e SECRET_KEY_BASE=secret \
  -v /Users/adnan/rubydev/openproject/pgdata:/var/lib/postgresql/9.6/main \
  -v /Users/adnan/rubydev/openproject/logs:/var/log/supervisor \
  -v /Users/adnan/rubydev/openproject/static:/var/db/openproject \
  openproject/community:8

Then copy the APP_PATH content to local folder: 

sudo mkdir -p /Users/adnan/rubydev/openproject/app
docker cp -a -L openproject:/usr/src/app/. /Users/adnan/rubydev/openproject/app/

#Remove the current container
docker stop openproject && docker rm openproject

#Re-create the container but now with volume linked between APP_PATH and copied local folder.
docker run -d -p 8090:80 --name openproject -e SECRET_KEY_BASE=secret \
  -v /Users/adnan/rubydev/openproject/pgdata:/var/lib/postgresql/9.6/main \
  -v /Users/adnan/rubydev/openproject/logs:/var/log/supervisor \
  -v /Users/adnan/rubydev/openproject/static:/var/db/openproject \
  -v /Users/adnan/rubydev/openproject/app:/usr/src/app \
  openproject/community:8

Starting container now taking longer time and it is failing to app loader timeout from Apache --> Passenger --> App start (Load Application). 

It suggests: "increase the spawn timeout (currently configured at 90 sec), or find a way to lower the server's resource utilization."

But failed to find how to increase it to meet the need. 

Any suggestions or success in making other way work?

For future users who may stumble upon this through google: There now is a way to develop OpenProject using docker.
It's simply a matter of bin/compose up now and you're done. Code can be modified locally and will be reloaded automatically.

See: https://docs.openproject.org/development/development-environment-docker/