I'm trying to gauge the importance of various collaboration scenarios... I hope you can spare a moment to consider the following scenario, and let me know your thoughts :-)
You publish a typeface family, "Alice," with 12 weights of roman and italic, covering full Latin, Cyrillic and Greek, under a 'libre' license. You publish all source files - FontLab VFBs including interpolation master outlines, OpenType feature files, and hinting files.
A well known competitor downloads the font's source files and changes the font into a new type design, "Bob," that looks much different. This is high quality work, and includes some fancy OpenType features, but the fonts only cover basic Latin characters. The company publishes "Bob" 8 OTF files, for roman and italic styles in 4 weights. They do not publish any source files, no interpolation masters, no OpenType source code.
You meet a client who likes Bob, and would like to hire you to extend "Bob" into full Latin, Cyrillic and Greek.
I wonder how useful it is to have access to the same kind of source files for "Bob" that you published for "Alice."