Affiliate Marketing Consultation

Hello I am in the process of launching an affiliate network where advertisers and publishers will have the possibility to register in order to open their accounts. It will be something like zanox, cj etc. However, I do have a lot of clients with websites, and I have my own websites. I guess that some of my clients will not be interested in joining my affiliate network, but might be interested in having their own affiliate marketing program. So, I would like some advice on a simple yet complete affiliate program software, open-source, that I can own full right to modify, improve, etc. I would like a stable, simple, but also robust and complete software. Also, it would be good to use a software where I could easily configure new clients. I would set-up each client in a sub-domain like [login to view URL], [login to view URL], [login to view URL] But when I think about this, I wonder if this is not getting to close of the affiliate network business; if so, it might be better to just create some kind of business model where these clients do not have to pay commission for performance, but, just some kind of monthly or yearly fee for maintenance or hosting of their affiliate program. PS: I already have the software for the affiliate network so this is not a problem PS 2: I already have a software for affiliate program called idevaffiliate but its not very good to handle more than one client.