Thanks to media compression advance and prevalence of broadband Internet, diversified multimedia network applications in e-commerce systems are more vigorously developing than ever. The most attractive IPTV services are emerging to be deployed by peer-to-peer (P2P) architecture to achieve scalability over Internet. However, the intellectual property rights (IPR) of valuable IPTV content distributed over P2P networks are more needed to be considered. To effectively apply digital rights management (DRM) for the P2P IPTV services is definitely an important issue. In this paper, we propose an effective P2P IPTV DRM architecture for e-commerce systems based on the standards from Open Mobile Alliance (OMA). A cost-effective key distribution mechanism with leverage between DRM protection strength and system/network loading is further proposed to improve OMA DRM frameworks for P2P IPTV applications on the opportunistic multicast overlay to overcome the peer churns of leaving and joining. The simulations and experimental results demonstrate that the cost-effectiveness of proposed P2P DRM schemes in preserving both of IPR protections and QoS/QoE for P2P IPTV services for e-commerce systems.