If you have a PowerPC, there is a CGX AGA driver for it, but to be honest theres little point.
If a program actually requires a graphics card, the chances are it'll want at least highcolour graphics, and unless the CGX driver has a HAM8 mode, the program still won't work (no modes to show in the screenmode requester).
Even if it DID have a HAM8 mode, it would be so slow as to make the program unusable.