It might be worth reaching out to maintainers of Linux’s ARM port or Russell King, the lead maintainer for Linux’s port to the ARM microarchitecture. I’d imagine he’d be amenable to helping other open source projects get access to access to suitably licensed ARM documentation, headers, as well as having contacts inside ARM.
The Linux Foundation may be another good resource. Their NDA Program helps open source developers gain access to developer documentation that’s all too often covered by non-disclosure agreements in a way suitable to all parties. ARM is listed as a supporting member of the foundation; I’d be surprised if they the two groups hadn’t already worked together to get the docs, code, and/or headers required for porting to their processors.
 http://lists.infradead.org/mailman/listinfo/linux-arm-kernel/  email@example.com  http://www.linuxfoundation.org/programs/developer/nda