[jh05013]

After reading this dozen of times, I've finally figured it out...

We have an FFR permission to use hololive original songs (not covers) except the ones listed in the appendix of the Derivative Works Guidelines.

Rhythm game charts are generally considered derivative works. Even with the guideline's definition, charting is definitely a creative endeavor so I'd say they count.

The part of the text that stumped me the most was the following in the "Guidelines for Use of Music" section:

We allow covers, adaptations, and remixes of applicable music (hereinafter to be referred to as “covers” for covers, or “musical derivative works” for adaptations and remixes).

* We consider derivative works to be creations born of fans’ ideas and creativity, based on our music. Therefore, we do not consider the reproduction of our music as is, or with modifications lacking creative input, to be classified as derivative works. Such use does not fall within the scope of the music or overall guidelines.

which does not seem to include charts.

However, this is in fact a slight mistranslation and the Japanese (original) text says (emphasis mine):

対象楽曲については、カバーソングとしての「歌ってみた」や、対象楽曲を翻案しリミックス等の二次的著作物（以下、対象楽曲を利用した「歌ってみた」またはリミックス等の作品を「二次的楽曲著作物」とします）を制作することができます。
※二次創作とは、当社楽曲に依拠しつつも、皆様の創意工夫・アイデアによって生み出される創作活動であると、当社は考えます。そのため、当社楽曲をそのまま複製したもの、改変に創作性の欠けるものは二次創作に該当せず音楽利用ガイドライン及び全般ガイドラインの対象外となります。

which permits all kinds of derivative works; the bolded "等の二次的著作物" translates to "derivative works such as ..." and "等の作品" to "works such as ..."

I think this link is the list of original songs.