While I am not a big fan of BG products (there are plenty of other more cost effective lubes & greases, etc), they claim their Synthetic ATF is Type-IV and 3309 compatible. They probably reversed engineered the product, just like Castrol and all the others. I doubt they paid royalties to Aisin-Warner to get the JWS3309 specification, though.
Remember, too, that 3309 is backwards compatible with most modern ATFs but the converse it not true.
I doubt very much that their ATF will hurt your tranny in any way. If it's shifting fine, don't worry about it.http://www.bglsi.com/ATF.PDF