I solved the issue. It wasn't about the bundled java version or the native libraries; I did try the former after forcing a redownload, and linked the latter to the respective /usr/lib folders anyway, to no avail. But then I found by the tried-and-true method of "googling some more" that, TL;DR: I hadn't quite installed XRandR as I thought (source: http://forum.lwjgl.org/index.php?topic=5742.0)

I had a similar problem today, similar symptoms: launcher works correctly, but upon hitting the "Launch" button, nothing is actually launched; the process remains in the Task Manager, but there's no window, and must be terminated manually.