GD which underlies GD::Graph, doesn't support vector graphics--or any of those output formats you mention--at all.

Whilst (I think) that those formats you've mentioned can incorporate bitmap images of the type GD produces, GD(::Graph) gives no support for producing those. You would need to seek out other solutions for creating those formats and including any images you created with GD::Graph into them. Relative to what gnuplot can do, this would involve lot of work on your behalf.

You might get on better looking at SVG & SVG::Graph, but I think you might still have the problem of having to also produce the ps,eps, emf format docs yourself and incorporate the SVG output into them.

That said. The licensing rules for gnuplot do not seem so onerous. Leave the copyright notice intact. If you modify it, change the version to reflect that, and include the patches you made along with the (binary) distribution. Why do you have to distribute it "under the same license as perl"?