Thanks for the latest update but you forgot to update the BCC .toc file.

Guildbook uses just a single .toc file as curse doesnt support the multi toc stuff yet, afaik anyways.

I have however updated the interface version in the toc which i did miss.

I am the author/maintainer of Skillet (for retail) and Skillet-Classic (for BCC and Classic Era). Curse has "sort of" support for multiple .toc files. You can use the Blizzard feature of multiple .toc files (addon.toc, addon-BCC.toc, addon-Classic.toc, addon-Mainline.toc), see this post and when you upload the file to Curse, you can edit the file and indicate which version(s) it supports.

I believe the BigWigs Package Manager can also be configured to generate multiple source files and upload different files for different flavors of World of Warcraft to a single Curse project, but in my Skillet / Skillet-Classic case, I have two different projects. The Skillet-Classic file can be installed on both Classic Era and Burning Crusade Classic.

Let me know if you have questions about how this all works and I'll do my best to help.