That is not how GPL works. Let's say you have derived work from GPLed source (DW). if (you publish binary of DW) then {you have to provide sources of DW under

That is not how GPL works. Let's say you have derived work from GPLed source (DW). if (you publish binary of DW) then {you have to provide sources of DW under GPL} Simply it does not apply to in-house (non-published) work. You are fine to keep it closed-source.