Generic is Premium, Dark, Responsive MyBB 1.8 Theme. It relies almost 100% on Bootstrap 3 with minimum overrides and it’s 99% tables. If you are familiar with Bootstrap 3 it’ll be like fun dealing with this MyBB theme. This is flat, basic version (default-blue), but it has three more color combinations: Green - Orange - Purple.
Code:
https://owlthemes.net/downloads/generic-mybb-dark-responsive-theme-theme/