For a quick example of an open source application, which does not grant the right to either modify or redistribute the code, look at PGP 8. It is free and source code is readily available, but not for redistribution or modification.

To my knowldge, the commercial versions of PGP also make source code available, but with the same restrictions. The source code is released so that it may be reviewed by the community for vulnerabilities and backdoors, not for modification and redistribution.

PGP is released open source, but is not a follower of the Open Source Initiative.