Any software startup that would accept an "intern" on the team is failing one test of viability. The last thing you need in startups is more than one level of hierarchy. [1] You don't want people to expend valuable mental and emotional energy trying to figure out if task X is "right" for a mere intern, or if it's really important not to have conversation Y in front of the intern, or (in general) whether or not the in…
If a team is missing some key capabilities for producing a functioning prototype, then it should bring someone else in and provide some equity.