Guild EXP Table.

According to the patch notes and all that, you can get your points and use them somewhere else, apparently.

I tested this a while back because the notes did make it seem like this is the case, but the GPs are lost. A character will always get just 500 GPs upon joining, doesn't matter how many they had before (unless at some point, you get to keep the points, say over 10k points, I only tested this with characters with 1-2k points).