>The others listed are grayed out so not available at this time.
Actually, all the listed payment options are available at the moment just not to everybody. I'll copypaste what Project-GC said on their official facebookpage about this, they also added that "mouse-over explanations" of this is on the to do-list:
"Those that are disabled only work for:
A) Specific currencies, by switching currency they may get enabled again.
B) For users in specific countries, usually only one single country.
Due to (B) we only enable them if we detect that the users IP is in a matching country, or that the Geocaching profile seems to belong to a matching country. Over 90% would otherwise just meet failed transactions."
This was a comment on this FB-post: https://www.facebook.com/ProjectGC/posts/3675214785869417