There are a few things which need to be pointed about.
- Since you are using (renamed) functions from SoftDev, you need to credit him. - This should not be called a GX rendering lib because you are doing all of your rendering into your own framebuffer and then just using GX to scale it into the xfb. All of your rendering functions (point, line, rectangle, texture) are software rendering into your framebuffer. (Which is horribly inefficient.) - The reason things are blurry is because you're rendering into your framebuffer first. All of those objects should be sent through GX.
- In general, for now people should probably be pointed to gx_supp.c/gx_supp.h by SoftDev from VBA for some easy RGB fb->xfb scaling routines using GX.