I am a bit confusing and I need your help to undertand my problem.

I have developed a web application (PHP, JQuery) for one of my customer.

Recently, my customer ask me to add a new feature permitting PDF to JPG conversion.

After web browsing, I have discovered that iMagick (Apache licence) PHP extension with GhostScript (GPL licence) is the only solution.

But, as my customer want to sell the web application to others companies, I have to use non-GPL licences.

By the way, this feature is OPTIONAL and the final user must download and install manually iMagick and GhostScript if he his interesting by using the PDF conversion.

Is there someone to tell me if the fact to use Imagick to convert PDF to JPG (and therefore use GhostScript) turns my current proprietary licence to GPL?

And what about if I don't use Imagick but call GhostScript using PHP exec() function?

Is there others non-GPL projects to convert PDF to JPG that I could use with PHP?

Any help would be greatly appreciated.