On Saturday, 11 June 2016 at 04:11:59 UTC, Joerg Joergonson wrote:
Are you using any of their source code from the vst sdk? If you hand re-write any of their source code, it is yours.
That could actually be considered to be a translation and a derived work. If you implement from a specification you might be safe, although some claim that APIs are copyrightable (questionable IMO).