I've had to wade through licenses on other projects, and the "viral" nature of GPL always leads to furious debate. Here are my comments:
Looks like a GUI wrapper over a command-line GPL program must also be GPL:
Both fortunately and unfortunately, that's not automatically the case, and the links you cite also show that. It depends on many factors, including how the wrapper and the GPL program communicate. FSF's GPL FAQ on
this issue acknowledges that the murkiness has to be resolved on a case-by-case basis based on the mechanism and semantics of communication. There
is a space for non-GPL programs to call GPL binaries and still be compliant with GPL.
Even if wrappers automatically had to be GPL-ed, I have to agree with Thomas Worth that it seems inaccurate to characterize RAWMagic as a wrapper. I don't know what the distribution of RAWMagic users, but it seems like there could reasonably be a significant fraction of the user base has no need for the vertical-stripes correction.
point is
a) you used GPL code in some of your versions
b) you sold them without releasing GPL'ed source
...
the OLD versions still are not GPLed! and this means: you are still ignoring GPL.
This is a clear violation of GPL, and something that Thomas Worth
must address and remedy. Unlike the above debate, direct integration of GPL code triggers GPL protections. You can't get around this.
Therefore, I suggest enforcing GPL compliance on all the postprocessing apps based on ML command-line tools.
Authors who do not respect the license will have their threads locked. If no corrective action is done within 1 month, their threads will be deleted.
Again, it's possible for non-GPL postprocessing apps to use ML tools while still being compliant with GPL, depending on the nature of the communication. However, reasonable people can disagree about where that line gets drawn. So, instead of dealing with the recurring debates over GPL compliance, simply only allow threads on this forum for GPL apps. Thus, unless Thomas Worth distributes RAWMagic under GPL, its forum thread will be locked/deleted regardless of the app's compliance with GPL.