Who owns this code ? Where you paid to develop this code ? If the OP was paid, his code belongs to google. In anycase a copyright will most likely apply to the user interface if it is a copycat of the Mac sparrow app.
If the OP manage to change it and eventually simplify it to make it significntly different, than the copyright won't hold and you own it as the author. The OP may then create his own brand. He should create his own app if the code doesn't belong to goggle.
I would suggest to make it a payed app, twice the price than Sparrow, and use the earned money to develop android, iOS and iMac version. If google offer to hire him, then request that the code is open source. Maybe Microsoft will have an offer to make too.
Of course Panos could also provide the app for free but he needs to earn a fair money for his work and for a living if we want him to continue and sustain the brand. Maybe another company could make an offer like Canonical for instance.