I'm personally sad about this, as I have been following Enemy Starfighter for years. It reminded me of Freespace 2 which is my favourite space sim of all time. The developer confirmed to me it's no longer coming to Linux officially, but he may team up with a porter in future.
Here's what they said in reply to me about Linux support:
@thenaughtysquid No, not anymore, sorry!— Mike Tipul (@tipul) April 9, 2016
And about the possibility of someone else porting it:
@thenaughtysquid That's definitely a good solution I'd consider down the line. A few cool people have talked to me about it.— Mike Tipul (@tipul) April 9, 2016
I seriously hope he does get someone in to port it, as it looks awesome.
What is Enemy Starfighter?
Enemy Starfighter puts you in the cockpit of the universe's most terrifying interceptor and gives you command of a vengeful fleet of Imperial warships.
Enemy Starfighter seamlessly mixes third-person tactical control and first-person cockpit gameplay to create an intense one-of-a-kind action experience.