I understand your position but in this case in version 2, should not integrate the billing module. When we look more closely Opensource applications using the community to develop the product, thousands of free tester, then integrates the modules pay.
It might be more interested in letting users make a donation to support the team.
I recall that open source solutions exist and are completely free.
---> OpenSource and oriented to commercial exploitation.
You tell me why I chose ISPConfig? The answer is that I have been using version 2.0 and I am familiar with the software.
I was convinced he would still be free and the community has been actively developing improved after at least thousands of feedback from us.