A quick search on the web seems to suggest you shouldn’t oil a regular (finished) maple fretboard, but many suggest it’s fine for unfinished (roasted) ones.
Interestingly, both my electrics are maple (one of each)- I always put a bit of oil on my HB roasted neck, but it never occurred to me to oil the finished satin G&L. That would seem weird and pointless.
Maybe also a good time to remind folk that the appearance/feel of fretboards are really just eye-candy anyway 
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