Up until know, when evaluating GitHub's reaction, we assumed the other co-founders wouldn't have known about this.

If they had a similar thing happen a while ago where someone was let go, in a company that prides itself for employee retention no less, that changes our evaluation.

It just means they condoned Tom's behaviour knowing first hand that it was problematic and had been for a long time; essentially lending credence to Julie-Ann's statement that the culture was toxic.

Based on the response I'd say that there's a good chance the toxicity might have largely stemmed from the management team not wanting to oust a co-founder, so there's a good chance it's ""fixed"" now, but that still doesn't excuse their lack of inaction until now.