Running executables without using rosrun or roslaunch ??

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MY QUESTION :

Do ROS topics still properly communicate (subscribe/publish) in the following situation, even though I DID NOT run executables by rosrun/roslaunch?

If not, is there way to run ROS executables without using rosrun/roslaunch?

SITUATION :

By running catkin biuld, executables are created as (~/catkin_ws/devel/lib/PROJECT_NAME/sample_node)

If I try to run the execuatble as follows, it prints seemingly okay results on screen.

./catkin_ws/devel/lib/<PROJECT_NAME>/sample_node

(roscore runs somewhere anyway.)

NECESSITY :

I want to add ROS publish function in my pre-developed code, which cannot be run by rosrun/roslaunch because it contains other pthreads.