TITWOW syndrome, 'a-byāpāda': some translators inconsistently interpret that as "good will" or "free of ill will"

 What does this matter? 

It's like the difference between the silver rule and the golden rule.

example: SN 55.7 The golden rule and silver rule

It matters because the precise Dhamma instruction in the suttas, if we go by some translations,  on what to do when we see "byāpāda"  is unclear.

It's quite a different mental state to 

1. be actively engaged with sending thoughts of good will towards specific groups of living beings,

2. Or to dwell in a mental state where one does not have to actively engage in thoughts about other living beings, but simply dwell peaceful and free of hatred, animosity, aversion. 

Which is it?

The Theravāda commentaries seem to believe a-byāpada (non ill will) and metta (friendliness) can be treated synonymously in most if not all situations.

There are about 150 sutta references to byāpada in the nikāyas, and I'm looking through them all right now. 

So far, I've seen some instances where it's definitely the silver rule (freedom of non ill will rather than "good will"),

and most cases either "non ill will" or "good will" would fit the context.

 Given the ambiguity, the best translation choice is the most versatile one

"Non ill will" or "freedom of ill will" is more versatile, because both silver rule and golden rule are options. 

Good will is a type of non ill will.

But if you lock yourself into translating byāpāda as "good will", 

you've restricted the interpretation to only the golden rule, blocking the possibility of the silver rule. 

One has to have good will directed toward other living beings,

one no longer has the option to dwell free of hatred, not thinking of any living beings.

byāpāda = ill will
✅a-byāpāda = non ill will, non hatred, or free of ill will, etc.
⛔a-byāpāda should not be translated as "good will"

Why do some translators choose "good will" as the translation for a-byāpāda?

Not always, but often because of TITWOW Syndrome