Hi.
It’s not possible to edit this field at the moment, but there’s a workaround.
Edit your product and enable “Show Button Only” option (“Appearance” metabox on product edit page). When this option is enabled, no additional product info is displayed (including subscription information).
Then create a page in WordPress with your product description and add product shortcode to your page. You can write any text you like there. E.g.:
{your product description is here}
I will make a monthly donation of:
[asp_product id="123"]