Could a glyph of warding be used for positive effects for allies?

@ChrisPerkinsDnD could a glyph of warding be used for positive effects for allies, like healing or buffs, or only "to harm" opponents? #dnd

— Kelly Clemmer (@kellyclemmer71) January 23, 2016

I think that's a very clever use of the spell, though clearly not its intended use. https://t.co/qJvv2yc86r

— Christopher Perkins (@ChrisPerkinsDnD) January 23, 2016