A big part of their switch seems to be a result of interpersonal issues with the X-Tag creators. After I left on less-than-good-terms with a handful of folks at Mozilla, they decided to ditch a library that makes components small, modular, and DRY, for what appears to be spite. The new Brick code base is over 2x heavier (despite being billed as a "lightening" move), each component is 40-60% larger (with a ton of repetition and use of X-Tag code), and the browser compat range has been reduced greatly.

They never reached out to the X-Tag team before posting this - it contains glaring inaccuracies and negative sentiment toward X-Tag.

I'm deeply disappointed by their poor open source behavior, and general lack of courtesy.