Securit-Echat is covered by the Mozilla 1.1 Public License without the Netscape-specific amendments.
To see the exact text of the Securit-Echat license go here.
To read Securit-Echat as an example of capability-based security, in which the code is thickly wrapped with text describing its operation, go here. Note that this document also includes instructions on how to use Securit-Echat.
To get Securit-Echat as a source text file that can be run directly on E or DaffE, go here.