I cloned the directory into my catkin_ws/src directory, then ran $ catkin_make, which resulted in the following CMake Error:

-- +++ processing catkin package: 'openpose_ros_msgs'
-- ==> add_subdirectory(openpose_ros/openpose_ros_msgs)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Generating .msg files for action openpose_ros_msgs/GetCrowdAttributesWithPose /home/mda-linux/catkin_ws/src/openpose_ros/openpose_ros_msgs/action/GetCrowdAttributesWithPose.action
CMake Error at /opt/ros/kinetic/share/genmsg/cmake/genmsg-extras.cmake:263 (message):
Messages depends on unknown pkg: gender_and_age_msgs (Missing
'find_package(gender_and_age_msgs)'?)
Call Stack (most recent call first):
openpose_ros/openpose_ros_msgs/CMakeLists.txt:36 (generate_messages)

-- Configuring incomplete, errors occurred!
See also "/home/mda-linux/catkin_ws/build/CMakeFiles/CMakeOutput.log".
See also "/home/mda-linux/catkin_ws/build/CMakeFiles/CMakeError.log".
Makefile:6648: recipe for target 'cmake_check_build_system' failed
make: *** [cmake_check_build_system] Error 1
Invoking "make cmake_check_build_system" failed

Will I be able to simply remove the lines within the CMakeLists and package files that call for GetCrowdAttributesWithPose (I don't need it), or is the solution not that simple?

please move msg/srv definitions into openpose_ros_msgs/openpose_msgs project (subfolder)