If you don't owe any taxes, do you still have to file a tax return by April 15th?

that depends...what does "don't owe" mean? Are you working under the table? Are you getting a commission only? Are you using barter? are you counting up your tips? cause all those ways yes you still have to pay your taxes and file by April 15.

the deadline is 4/15/2014, with an extension, 10/15/2014

if you don't make it by that date, anytime it is filed it is late

that will cause late filing penalties to be assessed and altho it states that the penalty is 10% of the amount owe, it seems to assume that if you don't owe, there is no penalty,

IRS can assess $100 penalty anyway, doesn't happen often

Owe, 0, refund doesn't matter if you meet the filing requirements.

Legally yes if you have income above your filing requirement,, but there's no penalty for being late.

no