Amazing, isn't it!
In the 90's Braathens bought "Malmö Aviation" which flew under the TF code. But TF wasn't merged with BU and when SK bought Braathens, the family kept Malmö Aviation, which recently got rebranded Braathens. So still norwegian, still same family owner!
I flew the orignal Braathens on MMX-FBU in in 1992, on what I believe was my first ever logged non-charter flight. I vivdly remember being blown-away when they didn't charge for coffee&cognac after the meal.