Source for PD {ba,k,c}sh

[Bill Poitras]

Where can I get a version of the sh, bash, ksh or csh which I can then
use in a commercial program?  I am going to be writing a scripting facility
for a program that I intend to sell, but instead of writing one, I want to
modify an existing one.  I want to know where I can one, as well as the 
copyright restrictions on it.  Any help will greatly be appreciated.


+-----------------+---------------------------+-----------------------------+
| Bill Poitras    | Polygen Corporation       | {princeton mit-eddie        |
|     (bill)      | Waltham, MA USA           |  bu sunne}!polygen!bill     |
|                 |                           | bill at polygen.com            |
+-----------------+---------------------------+-----------------------------+