Filk Song: As noted on the main page, a number of IOSYS' songs can be thought of as being in the parody-filk style (credit goes to the Touhou Wiki):note For the sake of not having to worry about YouTube videos breaking at a later date, no links to the examples will be provided. Go look them up yourselves.
"Alienation" = "Shame" by Shuuchishin
"Autumn's Soldiers — Aki Sisters" = "DANZEN! Futari wa Precure" from Pretty Cure
"Saint Marisa's Gift" = "Rudolph the Red-Nosed Reindeer"
"Satosatorirasatosatorirasatorira Daibakuhatsu" = "Yuriyurarararayuruyuri Daijiken" from Yuru-Yuri
"Screaming Cool Match" = "Zetsubou Billy" from Death Note
"Song for the Cruelty of the Hell of the 60 Year Flowers of Sin" = "Saintly Girl Territory" from Rozen Maiden
"There Are No Bombs" = "There Are No Umbrellas" by Yousei Inoue
"The Traveling Emotions of Love At A Moon-viewing Hot Spring" = "Usagi" (a Japanese children's song)note This one seems like kind of a stretch; however, because it is listed on the Touhou Wiki, it's listed here
"The Ultimate Yakiniku Restaurant! Orin's Hell Mansion!" = "Love Dial 6700" by Finger Fivenote Partial parody; listen to the first 30 or so seconds of "Love Dial 6700" and compare
No Export for You: There's nothing stopping non-Japanese Touhou fans from buying IOSYS's music... except for the one minor detail that almost none of the stores that stock their material (including their own) ship internationally. Mandarake is about the only online retailer that (a) carries their music and (b) does ship to the U.S.