Is wooxy not allowed anymore

Ya better not touch it.

Until it doesn't give you any advantage above other players, you won't get banned for it.

Riot doesn't support 3rd party, use at your own risk

Only you can see the Wooxy skins (unless someone else has wooxy and that skin installed) also the custom skins are usually lower quality than actual skins and there is a slight risk of virus/malware from downloading said installer and skins so I don't think Riot's losing much money.

If you want to get it, I recommend downloading the installer and custom skins to a thumbdrive using a computer you don't care getting viruses on (I always use library computers when downloading insecure content) and moving the files from the thumbdrive to your computer.

Of course, Wooxy is a far better option for free skins than anything that claims to just give you free skins in exchange for your account info.