BGT is kind of at the core of the BWP. It enables you to smoothly transition between all three games (BG1, BG2, ToB) and to use features in BG1 that were only available in these later games.
BWP, the Big World Project, as the name says, is a community project to make all the available mods as compatible with the BGT and each other as possible, and to basically provide the best installation order so you won't make your game unplayable by accidentally installing mods in the wrong order. It is more of an installation guide, but it does come with an installer.
To give you a better idea of what the BWP does and aims at you might want to read this guide here:
http://www.shsforums.net/files/file/534-big-world-english-guide/
On this page you can find several files (installation guide, installation pack, language packs etc.) related to the BWP:
http://www.shsforums.net/files/category/72-big-world-project/
I think the installer is still working, though I've never used it myself. I usually install mods manually using the guide as, well, a guide to get a conflict-free installation.