Please note that ThemeForest offers purchase licensing per single end product. There is no other option for licensing I can set/choose (such as bundle option), unfortunately.
I license all of my products the same as WordPress, 100% GPL.
If I may advice, I suggest installing the theme on a WordPress multisite setup with subdomains, if that’s possible. That way you should be able to use the theme multiple times and yet that doesn’t seem to violate ThemeForest licensing.
In case you decide to use my 100% GPL licensed theme on multiple websites (subdomains), I would like to ask you to consider supporting me by purchasing several licenses :)