This is all custom, so it's free to use for your game, if you can read french feel free to read this : -maker.fr/index.php?page=forum&id=10361 (it's the explanation of his stop, for non-french : stop cause of a boyfriend, no time to spend on making anymore, give the source of the game for the community)
I don't know if this is classic "deja vu" tilesets for you, because they are old (2004-2009), but the quality is really high so i decide to share this with the source on this forum because they were not here!
I'm not aware of the intellectual property of the RPGMXP RTP, but the tilesets he provides are in the same style, so I don't know if it's a problem, I woukd say no because a lot of games creates custom graphics for a Pokemon game in the same style than originals nintendo games, and they are doing money with the game (Pokemon Revolution Online for example).
So i think if you credit Benben, you can use freely the graphics for a commercially use, but personally I don't think it's correct to use only these graphics and make money with, if you have the pretention to sell your game, it's better to custom and add features to the actual pack (but it's only my point of view).
I'm checking the tilesets, and I don't find tons of rpgmaker graphics, i only see references to the rpgmxp universe with the statues of RTP mobs, original plants of RTP customs in differents size, ...
Wow I thought some of these tiles were lost forever. I have the tiles from the second screenshot and used the tree tile from that screenshot extensively. Thank you for its origin. I will look into this further