If you're seriously concerned with the legality (side note: legality in what jurisdiction?) of implementing something like that you should spend a couple hundre

If you're seriously concerned with the legality (side note: legality in what jurisdiction?) of implementing something like that you should spend a couple hundred bucks and chat with an attorney. Unhelpful, I know, but it seems like you have legitimate cause for concern, especially if you're located in the US, and HN isn't a source for legal advice regardless of the quality of commenters on the site. This is doubly true since the complexity of your question is likely far greater than you might anticipate, as is often the case with legal concerns, and likely not easily addressed here. So basically, if you're seriously concerned about legality: consult with an attorney. If you can't, or don't want to, spend the money to do so: don't write the library, or at a minimum don't publically distribute it. And if course, none if this is to be construed as legal advise, yada-yada, etc.