the3dfxdude wrote on 2023-02-04, 04:22:
and is still using dosbox code
This would force the source and binaries of vDOS to be distributed under the terms of the GPL v2, according to section 2b. In-house use is still OK, though, because the GPL restrictions only apply if you distribute the program.
the3dfxdude wrote on 2023-02-04, 04:22:
So I don't see it's worth the time to argue with him over 0.01 euro per copy.
Yes, this seems to comply with section 3b of the GPL.
the3dfxdude wrote on 2023-02-04, 04:22:
Now if instead he no longer provides source
This would violate the GPL, as it does not comply with section 3 at all.
the3dfxdude wrote on 2023-02-04, 04:22:
and charges 50 euro to register to remove the nag screen,
This is fine, according to the book. No clause in the GPL forbids that he adds nag screens to the software. You are free to add/remove any feature you want (maybe except removing the display of copyright notices). But at the same time, as the resulting product is to be distributed under the GPL (as already established), the user is entitled to get the source code for no more than the physical cost of the transfer (which is likely also true, but only for the old version). The source code itself has also to be licensed under the GPL, so the user has to be allowed to modify the software by removing the nag screen and re-publish this as forked version, again under the GPL. I don't think the author of vDOS would be happy about that, though.
There is no provision in the GPL that forbids the author to charge 50€ for the service to disable the nag screen, the idea being that this is solved by the market: Either the price is fair, or the user can hire an independent software developer for a reasonable price to adapt the software to your needs (i.e. remove the nag screen). If there are any license issues preventing the user to have an independent software developer remove the nag screen, the distribution of a work derived from a GPL product was not permitted in the beginning.