The man leading the buying group, Chisholm, hasn’t spoken much publicly since the announcement and is a bit of a mystery man. (The press release for the deal calls him a “lifelong Celtics fan and Boston-area native.”) He’ll be investing in his personal capacity, not through his firm, Symphony Technology Group, and is assuming responsibility for one of the most historic franchises in NBA history with a record 18 banners. The Chisholm takeover, as currently constructed, is not guaranteed to go through. The existing deal framework will test the NBA’s private-equity ownership rules.