Will development of ModPlugin ever be restarted, not only to be compatible with modern browsers (such as Firefox, Chrome and IE11), but also to take advantage of all of the format support and playback fixes of OpenMPT?
I personally think that bringing back ModPlugin in a more modern format would be an amazing idea. Obviously, the actual OpenMPT will take priority over this, but it definitely seems like it is worth looking into.
We have no intent to resurrect ModPlugin at all.
All browser vendors are currently phasing out native plugin support in their browsers in favour of more modern and secure technologies like asm.js or NativeClient. Mobile browser tend to not even support native plugins at all.
libopenmpt can already be compiled to asm.js via emscripten since quite some time now, and works just fine.
There is the already mentioned chiptune.js https://github.com/deskjet/chiptune.js
(based on libxmp and not OpenMPT/libopenmpt) and its successor, chiptune2.js (which uses an emscripten compiled libopenmpt) https://github.com/deskjet/chiptune2.js
(demo here: https://deskjet.github.io/chiptune2.js/
The problem though is that those have to be coded per-website, and Java has many of problems of which I presently do not have the stamina to go into detail.
Besides, OpenMPT was built on the original ModPlug Tracker, which itself was built on ModPlug Player, which itself was built on ModPlugin. With some reverse engineering and the new code, ModPlugin could be back up and running.