Oh, I think I figured it out. I just join my two queries with UNION

select b.user_id
from bids b
where b.project_id=95 -- current project
union
select pc.from_id as user_id
from projectclarify pc
where pc.project_id=95 -- current project
and pc.from_id != 269 -- project owner id
and pc.from_id != 2 -- poster_id