Sources

As of July 2005, the sources for the CD-i Emulator program amount to over 70,000 lines of C++ code in over 350 files, written in my private time over a period of several years. They will be available at some future date.

References

I found the following publicly-available references extremely helpful:
SCC68070 User Manual 1991, Parts 1 and 2 (hardcopy)
Complete description of 68070 processor used in most Philips CD-i player models.
MC68341 Integrated Processor User Manual (online)
Complete description of 68341 processor used in several portable CD-i player models, except for the basic CPU32 instruction set.
CPU32 Reference Manual (online)
Complete description of the CPU32 instruction set implemented in the 68341 processor.
Motorola MCD212 Video Decoder and System Controller (VDSC), Advance Information (online)
Complete description of CD-i video hardware used in newer CD-i player models.
Motorola MCD221 CD-Interface and Audio Processor (CIAP), Technical Summary (online)
Somewhat high-level description of CD-i cd+audio hardware used in newer CD-i player models.
M48T08/M48T18 TIMEKEEPER® SRAM (online)
Complete description of CD-i NVRAM hardware used in many CD-i player models.
Microware OS-9 2.4 Documentation (online)
Complete description of base component of CD-RTOS operating system used in all CD-i players.
Many of these are available from the ICDIA website at www.icdia.co.uk; the CPU32 documentation is available from the Freescale Semiconductor website at www.freescale.com.