Is there a way to set defaults for package.xml (Maintainer name

edit

Yes it is. See the output of catkin_create_pkg --help

catkin_create_pkg --help
usage: catkin_create_pkg [-h] [-s [SYS_DEPS [SYS_DEPS ...]]]
                         [-b [BOOST_COMPS [BOOST_COMPS ...]]] [-V PKG_VERSION]
                         [-D DESCRIPTION] [-l LICENSE] [-a AUTHOR]
                         [-m MAINTAINER] [--rosdistro ROSDISTRO]
                         name [dependencies [dependencies ...]]

Creates a new catkin package

positional arguments:
  name                  The name for the package
  dependencies          Catkin package Dependencies

optional arguments:
  -h, --help            show this help message and exit
  -s [SYS_DEPS [SYS_DEPS ...]], --sys-deps [SYS_DEPS [SYS_DEPS ...]]
                        System Dependencies
  -b [BOOST_COMPS [BOOST_COMPS ...]], --boost-comps [BOOST_COMPS [BOOST_COMPS ...]]
                        Boost Components
  -V PKG_VERSION, --pkg_version PKG_VERSION
                        Initial Package version
  -D DESCRIPTION, --description DESCRIPTION
                        Description
  -l LICENSE, --license LICENSE
                        Name for License, (e.g. BSD, MIT, GPLv3...)
  -a AUTHOR, --author AUTHOR
                        A single author, may be used multiple times
  -m MAINTAINER, --maintainer MAINTAINER
                        A single maintainer, may be used multiple times
  --rosdistro ROSDISTRO
                        The ROS distro (default: environment variable
                        ROS_DISTRO if defined)

If you want to "permanently" fix some of these settings for your on your machine it's probably the easiest way to add a bash alias to your ~/.bashrc file as @ahendrix suggested in his comment:

alias my_create_pkg catkin_create_pkg -l GPLv3 -a nobody@nowhere.com

Then call it anywhere like

my_create_pkg my_new_package_name roscpp other_depending_package