I tried doing some work with their code base around 5 or 6 years ago and at that time it basically didn't work out of the box and had no tests. Or at least their released code didn't.
Some of the problems were actual bugs that seemed odd in a production code base, and others were because they had stripped everything relating to some paid services they used for search or indexing or stuff that I don't remember.
In general it was a huge PITA to do anything with compared to what the leadership was hoping. (That it's be like the WordPress in terms of required investment was what they'd been hoping for.)
Some of the problems were actual bugs that seemed odd in a production code base, and others were because they had stripped everything relating to some paid services they used for search or indexing or stuff that I don't remember.
In general it was a huge PITA to do anything with compared to what the leadership was hoping. (That it's be like the WordPress in terms of required investment was what they'd been hoping for.)