My copy of Adapt Builder doesn't have Theme Customisation - is that a Learning Pool only feature? Will it be open source in the future?
Theme editing isn't currently available in the open-source authoring tool. Any features you see linked to the name 'Adapt Builder' (rather than the more generic 'authoring tool' moniker) should be assumed to be Learning Pool-specific, and therefore not available to the open source community.
This being said, theme customisation is on the open-source roadmap, and is a feature which I believe Learning Pool intend to lead on for obvious reasons. I'll let Brian or Dennis comment further on this.
See this thread for more discussion on the Builder/authoring tool topic.