The license used for all JMO Assets is the Unity Asset Store End-User License Agreement.
You can find it here (Appendix 1).
It does state that you can use the assets in a commercial application, without necessarily crediting me (Jean Moreno) or JMO Assets in it (although I don't mind if you do, just warn me).
Note that the assets must be embedded into the application, so it is forbidden to open-source your application (unless you exclude the assets from the source).

Follow these steps to use the spawn system:

1. Create an empty GameObject in your Scene
2. Add the CFX_SpawnSystem component on it
3. Drag/drop your effect Prefabs from the Project panel to the CFX_SpawnSystem Inspector
4. (optional) Input the number of instances you want to preload¹
5. Open the Script that will spawn the effect
6. Use the line CFX_SpawnSystem.GetNextObject(myPrefab); to get the next instance² in the preloaded pool where myPrefab is a GameObject property referencing the same prefab you dropped on the CFX_SpawnSystem inspector
   This method works the same as if you used Instantiate(myPrefab);
7. (optional) Set the position of the instance effect this way:
   
   GameObject instance = CFX_SpawnSystem.GetNextObject(myPrefab);
   instance.transform.position = myPosition;

1. The number of preloaded instances should be equal to the maximum number of times your effect will be shown concurrently on the screen

2. The next instance in the pool is not necessarily unused, that's why you need to carefully set the correct number of instances to preload

This is due to Unity's automatic culling system for the Particles, which deactivates the simulation when an effect is off screen and reactivates it when it gets back in the view, leading to problems when it affects only certain children of that effect or if it was supposed to be destroyed.
You need to disable the automatic culling feature by editing the Particle System's inspector.
One of the easiest known way to do that being to activate the 'Sub Emitters' module but without adding any actual subeffect.
You should see a small (!) sign near the name of the effect telling why automatic culling is disabled.

If the error is:

ERROR: Shader error in 'Toony Colors Pro 2/User/...': Too many interpolators used (maybe you want #pragma target 3.0?)
ERROR: Shader error in 'Toony Colors Pro 2/User/...': Arithmetic instruction limit of X exceeded; Y arithmetic instructions needed to compile program
THEN: You have selected too many features in the Shader Generator, and the shader can't compile properly.
You can try to increase the shader target level if your target platform will support it.
If you have to stick to the selected shader target level, then you should gradually remove features to see when the shader can compile properly.

Sometimes the custom Material Inspector doesn't load right away. Unselect and select back the material/object for it to show.
If the problem persists, make sure that:
- the shader compiled successfully
- the script TCP2_MaterialInspector exists, is compiled successfully and is in an Editor folder