Non devi distribuire il codice sorgente a tutti finché qualcuno non lo richiede . Ma se scegli di non distribuirlo insieme all'eseguibile, devi fornire una "offerta scritta" per il codice sorgente, che presumo dovrebbe includere le istruzioni su come contattarti e chiederlo.
Dal preambolo di GPL v2:
You must make sure that they, too, receive or can get the source code.
Quindi va bene se non ricevono il codice sorgente subito, a patto che tu fornisca loro il modo di farlo in seguito se lo desiderano.
Suppongo che tu stia già distribuendo il programma in forma eseguibile, quindi la parte rilevante del corpo principale della licenza è:
3 You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)
Tutto il mio enfasi.