Check Base.USE_GPL_LIBS before loading GPL code

[simsurace]

Could we check for the value of Base.USE_GPL_LIBS and only load the GPL code in this package (which seems to be all of it) when it evaluates to true? This would allow one to easily check whether a given application/package works when Julia is built without GPL libraries.

[peteristhegreat]

Agreed. The license for this package should probably be changed to be the same as librmath (GPLv2) unless a special exception is requested/amended onto the license of librmath.