Talk:GUMI/@comment-35507372-20190514181900/@comment-53539-20190515094340

https://vocaloid.fandom.com/wiki/Controversy_Concerns/POCALOID_and_illegal_modifications#XSY_modding

They basically modified the software to allow XSY with every vocaloid voicebank, including some very un-recommended ones such as language ones. Check out the Cross-Synthesis page because it lists the legit allowed ones. You only get problems when you publish work, the modding stuff is generally not cared when its done in private.