I think by any reasonable interpretation of the GPL, they are still breaking it by using a wrapper around the binary.
Why? Well... well, the GPLv2 does apply to them. There's no question about that by distributing Dosbox with or without source modifications, they have accepted the licence (see section 5)
The next question is whether by putting a wrapper around Dosbox they have broken it. Well, by my interpretation, they have:
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
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Progra […]
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These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works. But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.
It says nothing about /how/ it was made - whether via modifications via the source or otherwise, just about distributing modifications. As such, I think it's pretty clear that by putting a wrapper around Dosbox and distributing the modification requires them to release the source of the wrapper as well, as without the wrapper it doesn't have the same functionality. Ergo, they are still breaking the GPL.
Of course, if the developers are fine with it, nothing can be done, and even if they aren't it's certainly going to be an issue doing anything about it.