I have contacted Simon Parzer, and here's what he replied:
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Hello back. First of all, I appreciate your request. Unfortunately I see no real possibility of bringing Cave Story to the Dingoo A320. There are several reasons to it and I want to explain them to you.
1) I don't possess a Dingoo, so development would be cumbersome as I wouldn't have the opportunity to test anything on the real machine. Also, it has a different processor architecture than the PC or the GP2X (MIPS), so the chances that it works out-of-the-box are small.
2) As Cave Story is going to be released for Nintendo Wii this year (on the WiiWare channel), the political situation for a new freeware port is not very good. Currently I don't have permission to port Cave Story to new platforms. If you want to change that, talk to either Daisuke Amaya aka Pixel, creator of the game or Tyrone Rodriguez, the guy who owns Nicalis, the company that does the WiiWare port.
some pointers:
http://nicalis.com/blog/forums/ - Nicalis Forum
http://hp.vector.co.jp/authors/VA022293/ - Pixel's Homepage
3) I don't know if the Dingoo A320's hardware is strong enough - I suppose so (it has a stronger CPU than the GP2X which should compensate for the missing 2D accelerator).
If you have any questions or, more importantly, if you think you have a solution for me, you can always send me a mail - the address would be simon.parzer[AT]gmail.com"
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