The last uncorrupted version of cisc's licensing info for his "fmgen" lib states: "商用ソフト(シェアウェア含む) に本ソースコードの一部，または 全部を組み込む際には，事前に作者の合意を得る必要があります．" (see FM Sound Generator with OPN/OPM interface Copyright (C) by cisc 1998, 2003.)
If "google translate" did not screw this up completely, then any use of the code for commercial purposes requires cisc's prior consent.
I don't think that any project that builds on this code can use GPL (unless cisc has also issued some additional GPL license that I am unaware of).
The last uncorrupted version of cisc's licensing info for his "fmgen" lib states: "商用ソフト(シェアウェア含む) に本ソースコードの一部，または 全部を組み込む際には，事前に作者の合意を得る必要があります．" (see FM Sound Generator with OPN/OPM interface Copyright (C) by cisc 1998, 2003.)
If "google translate" did not screw this up completely, then any use of the code for commercial purposes requires cisc's prior consent.
I don't think that any project that builds on this code can use GPL (unless cisc has also issued some additional GPL license that I am unaware of).