SELECT text FROM all_source WHERE name = '<objectname>';

GRANT EXECUTE ON MOD03.M3LETTER TO AppUser;

create synonym appuser.m2letter for mod2k.m2letter;

grant all on mod03.m2letter to appuser;

sys@ORA92> CREATE USER	mod03 IDENTIFIED BY mod03_pass
  2  /

User created.

sys@ORA92> CREATE USER appuser IDENTIFIED BY appuser_pass
  2  /

User created.

sys@ORA92> GRANT CONNECT, RESOURCE TO mod03, appuser
  2  /

Grant succeeded.

sys@ORA92> CREATE OR REPLACE VIEW test_view AS
  2  SELECT * FROM dba_source
  3  WHERE  owner = 'MOD03'
  4  /

View created.

sys@ORA92> GRANT SELECT ON test_view TO appuser
  2  /

Grant succeeded.

sys@ORA92> CONNECT mod03/mod03_pass
Connected.
sys@ORA92> @ LOGIN
sys@ORA92> SET ECHO OFF

GLOBAL_NAME
----------------------------------------------------------------------------------------------------
mod03@ORA92

mod03@ORA92> CREATE OR REPLACE PACKAGE m2letter
  2  AS
  3    FUNCTION test
  4  	 RETURN VARCHAR2;
  5  END m2letter;
  6  /

Package created.

mod03@ORA92> CREATE OR REPLACE PACKAGE BODY m2letter
  2  AS
  3    FUNCTION test
  4  	 RETURN VARCHAR2
  5    IS
  6    BEGIN
  7  	 RETURN 'this is mod03.m2letter.test';
  8    END test;
  9  END m2letter;
 10  /

Package body created.

mod03@ORA92> GRANT EXECUTE ON mod03.m2letter TO appuser
  2  /

Grant succeeded.

mod03@ORA92> CREATE OR REPLACE PROCEDURE mod03_source
  2    (p_ref  OUT SYS_REFCURSOR,
  3  	p_name IN  VARCHAR2 DEFAULT NULL)
  4  AS
  5  BEGIN
  6    OPEN p_ref FOR
  7    SELECT text
  8    FROM   user_source
  9    WHERE  name = NVL (UPPER (p_name), name)
 10    ORDER  BY type, line;
 11  END mod03_source;
 12  /

Procedure created.

mod03@ORA92> GRANT EXECUTE ON mod03_source TO appuser
  2  /

Grant succeeded.

mod03@ORA92> CONNECT appuser/appuser_pass
Connected.
mod03@ORA92> @ LOGIN
mod03@ORA92> SET ECHO OFF

GLOBAL_NAME
----------------------------------------------------------------------------------------------------
appuser@ORA92

appuser@ORA92> SELECT mod03.m2letter.test FROM DUAL
  2  /

TEST
----------------------------------------------------------------------------------------------------
this is mod03.m2letter.test

appuser@ORA92> COLUMN text FORMAT A40 WORD_WRAPPED
appuser@ORA92> BREAK  ON type
appuser@ORA92> SELECT text
  2  FROM   all_source
  3  WHERE  owner = 'MOD03'
  4  AND    name = 'M2LETTER'
  5  ORDER  BY type, line
  6  /

TEXT
----------------------------------------
PACKAGE m2letter
AS
FUNCTION test
RETURN VARCHAR2;
END m2letter;

appuser@ORA92> VARIABLE g_ref REFCURSOR
appuser@ORA92> EXECUTE mod03.mod03_source (:g_ref, 'M2LETTER')

PL/SQL procedure successfully completed.

appuser@ORA92> PRINT g_ref

TEXT
----------------------------------------
PACKAGE m2letter
AS
FUNCTION test
RETURN VARCHAR2;
END m2letter;
PACKAGE BODY m2letter
AS
FUNCTION test
RETURN VARCHAR2
IS
BEGIN
RETURN 'this is mod03.m2letter.test';
END test;
END m2letter;

14 rows selected.

appuser@ORA92> SELECT text
  2  FROM   sys.test_view
  3  WHERE  name = 'M2LETTER'
  4  ORDER  BY type, line
  5  /

TEXT
----------------------------------------
PACKAGE m2letter
AS
FUNCTION test
RETURN VARCHAR2;
END m2letter;
PACKAGE BODY m2letter
AS
FUNCTION test
RETURN VARCHAR2
IS
BEGIN
RETURN 'this is mod03.m2letter.test';
END test;
END m2letter;

14 rows selected.

appuser@ORA92> CONNECT scott/tiger
Connected.
appuser@ORA92> @ LOGIN
appuser@ORA92> SET ECHO OFF

GLOBAL_NAME
----------------------------------------------------------------------------------------------------
scott@ORA92

scott@ORA92> SELECT text
  2  FROM   all_source
  3  WHERE  owner = 'MOD03'
  4  AND    name = 'M2LETTER'
  5  ORDER  BY type, line
  6  /

TEXT
----------------------------------------
PACKAGE m2letter
AS
FUNCTION test
RETURN VARCHAR2;
END m2letter;
PACKAGE BODY m2letter
AS
FUNCTION test
RETURN VARCHAR2
IS
BEGIN
RETURN 'this is mod03.m2letter.test';
END test;
END m2letter;

14 rows selected.

CREATE OR REPLACE PACKAGE MOD2K.m2letter AUTHID CURRENT_USER as
...

GRANT CREATE ANY PROCEDURE TO AppUser;