[Discussioni] posso modificare un prog GPL per conto mio?

[Francesco Potorti`]

Francesco Potortì:
   > Sì, ma io vorrei un riferimento a dove nel testo GPL c'è scritto
   > che lo posso modificare attaccandolo ad un programma proprietario.
   
Simo Sorce:
   Se l'uso nel privato non e' (volutamente) regolamentato e'
   semplicemente possibile farlo

Da quanto leggo nella GPL, in particolare articoli 4 e 5, capisco che
quanto tu dici non è vero.  In diversi punti, che cito sotto, si dice
esplicitamente che la modifica non è permessa, se non nei termini della
licenza.

L'articolo 2 esamina le condizioni necessarie, e per quanto ne capisco
sufficienti, a che il programma possa essere modificato.

Se queste condizioni sono in effetti sufficienti, allora posso
modificare il programma a casa mia e collegarlo con pezzi non
compatibili GPL, purché io rispetti le norme 2a e 2c.

io credo proprio che quelle condizioni siano sufficienti, ma mi
piacerebbe qualche commento sull'argomento.



Da gpl.txt:
================
Preamble [...]

These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

[...]

(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

0. [...]

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  

[...]

  2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

    a) You must cause the modified files to carry prominent notices
    stating that you changed the files and the date of any change.

    b) You must cause any work that you distribute or publish, that in
    whole or in part contains or is derived from the Program or any
    part thereof, to be licensed as a whole at no charge to all third
    parties under the terms of this License.

    c) If the modified program normally reads commands interactively
    when run, you must cause it, when started running for such
    interactive use in the most ordinary way, to print or display an
    announcement including an appropriate copyright notice and a
    notice that there is no warranty (or else, saying that you provide
    a warranty) and that users may redistribute the program under
    these conditions, and telling the user how to view a copy of this
    License.  (Exception: if the Program itself is interactive but
    does not normally print such an announcement, your work based on
    the Program is not required to print an announcement.)

[...]

  4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.

[...]

  5. You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.