Unknown plant, please identify

I have these little plants growing under our hazelnut tree not far from our neighbor's yard. I was wondering what they are and is it friend or foe? Thanks

 

Carpet bugle (Ajuga reptans), a purpleleaf form.

 

A search for [GOOGLE]Ajuga reptans invasive[/GOOGLE]

 

I like the way google search always manages to come up with things like this . . . :-))

 

Thank you! I guess I won't move it to my mixed border, in that case.