I think some updates are in order for this Wiki page in order to more accurately reflect the goals of the project: https://cwiki.apache.org/confluence/display/BIGTOP/Requirement+for+adding+a+new+component+to+Bigtop+distribution.
For starters, it should have a more prominent link on the Wiki and a summary on the project home page. Not only is it going to be an increasingly common question, but it's an important part of defining what "Bigtop" is really all about. I know when I first started on the project it was the first thing I looked for.
Second, we say projects have to be "Big Data"-related. Judging by other documents* and existing discussions regarding new components, it seems like we really mean to say "Hadoop"-related, and I think the extra focus would be good (having said that, I do think of Spark as Hadoop-related).