Best navigated at www.gameblibrary.com.
Usable as an API at data.gameblibrary.com.
Source available at github.com/nmaro/librarybdata
Most transcripts are autogenerated by youtube and could be much better.
To find transcripts to work on navigate to your favorite piece in the library and click on the "view raw transcript link on GitHub" link.
To suggest an improvement you'll need a GitHub account.
- Podcast transcripts! Not done yet because it's a lot of manual work :)