What are UST's?
An UTAU Sequence Text (UST) is basically digital sheet music that lets the UTAU program know what notes to play, how the notes should be sung, and what words to sing. Not only are there A LOT of components that go into making a UST but music theory is also used to make the correct melody and harmonies for a song. Because of this, it's ethical to give credit to the people who made the original UST's. As far as whether you can redistribute them, that will vary between each UST creator. As for me, you can totally do that as long as you give me credit. After all, UST distribution is part of the backbone of the UTAU community. Just make sure you at least change the tunings to make the UST your own in some way. It's kind of lazy if you don't change anything.
Composer: Mitchie M
UST's: (CV and VCV Japanese) felichanxx [I changed this quite a bit] (CVVC Delta English) ZaneChihuahua
Composer: cosMo@bousouP
UST's: Lmocinemod (I changed this quite a bit and added the talking parts.)
Composer: emon
UST's: HiepTran様 (Melody: I changed this quite a bit) and ZaneChihuahua (Male Melody and all Harmonies)
Composer: David Seville and Alvin and the Chipmunks
UST's: ZaneChihuahua
Composer: Triodust
UST: ZaneChihuahua
English Translations: Studio Klondike
Composer: れるりり (rerulili)
UST: たーさん (Taasan) and ZaneChihuahua (I changed a lot of these and added a lower harmony part)