'Broadcast' is treated differently in different dialects and shows signs of changing with time. Since the root is from the word 'cast', one available (first choice of the OE) past tense is 'broadcast', the other less preferred one is 'broadcasted'. However, the past participle (as used above in the post in question) is only given as 'broadcast'.

So the traditional English usage would be "has broadcast"

It's not a spelling error, it's a grammatical error ie using the past tense instead of the past participle.

Stu