Okay, here is some source if you or anyone else wants to do anything with it (no license attached to it right now, do what you will with it I guess?)
http://drastic-ds.com/temper_src_10_1_2012.tar.gz
http://drastic-ds.com/temper_src_2_12_2009.tar.gz
(now none of you can say I'm a proprietary code zealot who refuses to release source code until the day I day

)
I think the former should match the Pandora port while the latter should match the last GP2X/Wiz versions.
I can try to field questions but I can't promise I'll be able to answer everything. Some things will probably take some time for me to re-acquaintance myself with the code. I faintly remember some of the compatibility issues, I don't think much of it is very major except for Popful Mail which is a timing problem due to a lack of VRAM contention timing or something.
Just a note: I intended to originally port the new renderer to ARM ASM like the old one was. But I got frustrated trying to fit it in the registers and was being too much of a perfectionist which led to everything coming to a screeching halt. I don't think this is really terribly necessary for Pandora or maybe even Wiz, but if you want to get good performance on GP2X it can make a difference. Decent SGX performance is probably not very realistic without it. One thing about the new renderer is that with the way it works it's not too hard to add native rotated output, which would have been nice for Wiz and GP32. But the latter would definitely need ARM ASM.
I don't think there was an awful lot else I was going to do with it. At some point I wanted to port the OGG playback to the second core on GP2X but I don't think that was ever terribly necessary either and it's pretty moot now.