ninethousand/ninethousand-jobqueue — comment on commit e732ae4f5a7ebe27646ec8c3e32af8090254fef4
File:  line 0
By jessegreathouse:

The library has to be there in order for core functionality to exist. As a component, it needs to be self-sufficient, however I did create the possibility to add the cron library as a submodule so you have the option to load the cron class as a submodule or fork. This was also important because obviously the user cannot depend on me to keep the auxiliary library up to date.

https://github.com/ninethousand/ninethousand-jobqueue/blob/e732ae4f5a7ebe27646ec8c3e32af8090254fef4/lib/NineThousand/Jobqueue/Service/JobqueueControl.php#L31