The workshop is hosted by the ICFP conference so you need to register there, which is probably too late. But all the videos are available online and you can post questions in the OP link to Discuss, we will try to forward it to the workshop and later post the Q&A session on our channel (so subscribe)
https://www.youtube.com/watch?v=E8T_4zqWmq8&list=PLKO_ZowsIO...
BAP is not a competitor to IDA Pro or Ghidra, it's a platform for implementing automated analysis, while IDA and Ghidra are more like reverse engineering tools that are focused on human interactions. We do support IDA Pro so that you can run BAP analysis from it and have the best of two words. We will soon roll out the support for Ghidra too (the issue is created [1]).
What is a really great contribution of Ghidra, to my opinion, is the detailed specification of all supported ISA in Sleigh (their terse and concrete ISA specification language). Ghidra ships with about ~200kLOC of instruction descriptions and this is the most valuable contribution to the community. We're planning to support Sleigh in the nearest future, and I believe that Sleigh might become a standard de facto for instruction semantics specification.
