Yes, that's OK. he is the boss "for" in the sense of "because" is quite formal and literary-sounding. It is not usual in everyday English.
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SurferIs it in no context acceptable that the there be omitted? I intentionally left it out as I wasn't addressing a real/actual position but rather a quality in him.. ."boss" is a singular countable noun, so it normally needs an article or other determiner. However, there is an idiomatic sense in which "the" can be dropped and so you can say "He is boss". I