If the plots are or are nearly identical, then they are Copyrighted:
Copyright (C) 2011 Jeffrey Whitaker
Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notices appear in all copies and that both the copyright notices and this permission notice appear in supporting documentation.
THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
and
©2011, Jeffrey Whitaker; 2016 The matplotlib development team.
Jeffery Whitaker's 2011 claim and license allows for redistribution given the proper attribution.
The results(output) of a software program(unless stated otherwise in the EULA i.e. academic licensing), all rights belong to you. (Since the code is on github as a public open source repository, no such EULA restrictions apply)
As long as your data presented on the plots is unique, I do not see a copyright violation.
If they are not unique, give full attribution as required by license.
Infringement suits may be covered by fair use doctrine.
I would always suggest contacting a lawyer in IP matters.
None of the above should be considered legal advice, merely my informed personal opinions.
