I don't think you need to ask LL's permission to make and sell this at all. If LL didn't want people to do this kind of thing they would not have created HTTP commands in LSL the way they have. If they don't want web to in world communications they shouldn't have given us this capability. Asking them permission to use LSL commands would be like asking permission to teleport or something. It doesn't make any sense.
LL charges for advertising on their own web site. They have no authority over what you do on your own web site. The current TOS privacy rules explicitly recognize that LL has no authority over what residents do outside of SL. I have never, ever seen a TOS that even hints at prohibiting this kind of thing.
Now, will they like it? That's a different question. I can never predict what LL will bless with favors and what they won't. It's best to just make your product, put it out there and maybe they'll like it and politic with you and maybe they won't. If they like you then maybe you can get your own forum here like the blood liners have. Whether they like you or not isn't really the problem, though.
If they try to ban this product on you I would reccomend getting a lawyer.