Stef, Let's go forward in time. NativeBoost, Alien or FFI provide callbacks, I do some adaptation on my end, and out comes a pretty capable wrapper for the GNU Scientific Library. That sentence trivializes a LOT of work :( Details aside, is the wrapper code itself affected by GPL, or is it merely something unrelated that happens to invoke GSL if the latter is present on a system? What implications would that have for putting the wrapper in the inbox? This won't happen next week or next month, but depending on how easy it is to get going with callbacks, it shouldn't be years either. Bill