Maybe not the most bugfree one - and at least it is pruned to have a GUI-rewite (it might help to restrict functionality a bit more to make it easier to maintain).
https://github.com/GWRon/DigOf course it is open source under a nearly non-restrictive licence (zlib/libpng). It includes helpers (string, math), simple vector classes, tooltip-code, GUI-widgets (button, lists - select/slot/basic, panels, checkboxes, input, dropdowns, accordeon, sliders, scrollbars. dropdowns and lists might show scrollbars automatically. Drag'n'Drop-Support), event manager (GUI, Application framework ...), sprite classes + ninepatch support, bitmap font class (including "effect" support), sprite-atlas support, graphics manager (virtual resolution, fullscreen/windowed, ...) including renderer-path-"tryout", localization, logger, lua engine (with easier exposing of blitzmax stuff to lua and vice versa including blacklisting and whitelisting), a registry which sprites and other dig-stuff hooks into so you can easily retrieve stuff "globally"... and much more stuff.

Code should be "NG-compatible". As I use it for our game TVTower I fix compatiblity-issues as soon as I do an NG-64-bit release (basically I extracted the framework from that game's sources as it allows an easier re-usage).
bye
Ron