When you are an open source technology provider, you open every corner of the technology you provide, like I did. Surely this helps the competitors to check the solution you provide, what issues you face and probably offer better solution.
Here comes the question: should be we afraid of competition when go open source?
Would be interesting to know not only your "yes" and "no", but your answer on "why think so?"
FYI - you have a spelling mistake in your title, you used "completion" instead of "competition"
To answer your question: Don't be afraid, you're going to encounter competition no matter what you invest your time in if you're bringing something to market (open source or otherwise). Competition is healthy and it validates a need for the idea. If you don't have competition, then your odds of bringing a dud to market increase.
Instead of worrying about competition, focus on differentiation and staying 1 step ahead. You're going to have people who will copy your features - take it as a compliment and as a reminder that you should continue to evolve your project.