Part of the code is under GPL2

[bkmgit]

Pointed out in code review is that buffer.h and buffer.c seem to be derived from Houdini buffer.h and Houdini buffer.c which are available under GPL2 with a linking exception and originally came from libgit2

[jgm]

buffer was added by @vmg who at the time was working for GitHub, where this code was developed.
@vmg certified in commonmark/commonmark-spec#269 that the license was correct.

[jgm]

By the way @vmg is also one of the libgit2 contributors. Hopefully @vmg can comment here to clarify things.

[vmg]

The PR in commonmark/commonmark-spec#269 is the authoritative source for licensing information.

@vmg certifies by merging this PR that the license and copyright information are accurate.

I approved that PR and re-licensed the code under the same permissive license as the rest of cmark. There is no GPLv2 code in cmark because that would make the library useless.

[bkmgit]

Thanks. A related issue is the copyright notices on utf8.h and utf8.c

github#348

[bkmgit]

Associated pull request #483