OS X terminal "open" command and keeping focus on the command line
Use the -g flag.

From the man page:


  -g  Do not bring the application to the foreground.


Example: To open the folder at your current path, behind the current Terminal window:

open . -g




As a side note, it is often better to manually peruse the documentation for new commands, as the verbiage may be different from what you expect:


  i.e. "Do not bring the application to the foreground." vs. "Maintain terminal window focus."