On Tue, Dec 8, 2009 at 4:38 PM, Robert Greayer
Not to belabor the point (I hope), but consider the following situation -- if the current version of Pandoc, 1.2.1, were released under BSD3, not GPL, it would be obvious that the current version of hakyll could be released as BSD3 as well. After said hakyll release, the Pandoc maintainer would be perfectly within his rights to release an API compatible 1.2.2 version of Pandoc, this time licensed under the GPL. People installing hakyll with cabal might now be building a version of hakyll containing both GPL and BSD3 code. This is not under either author's control, and is perfectly allowable. If the person downloading chooses to redistribute the hakyll executable he's built, he must be aware of and comply with his responsibilities under the GPL, but those would be his responsibilities, not those of the original author of hakyll. (AIUI -- IANAL).
The compatible-API issue is very murky — it does indeed seem weird that creating an API-compatible BSD'd library would magically "release" users. I've seen other discussions regarding this, and about the sanest conclusion I've drawn is "ask your lawyer". :-/