Correct, most of the time MODS are GPL so you don't need approval to reuse these existing works. The approval gathering is pretty unique to the phpBB community and probably stems from the phpBBFM trobles from years back.
As it happens I also have an old copy of Custom Pages 0.0.2 and that does carry a GPL license, so no worries there
I have ported the custom pages mod to a module for my phpBB based CMS. My CMS system has an almost transparent API, so moving it to vanilla phpBB will be a snap once I have it working completely.
So far I have found that bbcode is broken because the old CMS it was designed for had a different bbcode parser, I will get it working with the regular phpBB bbcode parser tomorrow.
HTML doesn't work. Smilies do. It you just view pages.php you see a table of contents, click on a page in the list show that pages. Pages are added/edited in the ACP. It isn't much but it is a starting point. There is a dirty hack regarding the page id in the ACP for adding new pages, it functions but it is a nasty bit of code.
I'll PM you tomorrow when I have fixed bbcode and uploaded an archive for you.