Anyway - you can lie if you want to and I certainly won't judge you - but I didn't say you should lie or be a pirate. I said ignore the license. Big difference. (From your original post, it sounded to me like you probably don't have shareholders. Do you?)
Are you aware that vast numbers of small, medium and even larger size businesses are running SQL Server without the proper licenses? Are you also aware that Microsoft knowingly allows this to happen with a wink and a nod? Just like Windows and Office...until XP/2003 when they turned to activation. They didn't do that for SQL Server or many of their other products as far as I can remember. Could happen, but we'll see...
So yeah, advising you to do what millions of other business do too - I have no problem with that. (I also have no problem bribing the locals if that's the normal course of business. Don't think of me as immoral - I'm a realist. Big businesses squeeze everybody in one way or another, so if you can get away with it - it's great advice. The risk goes up the larger your company gets, obviously...)
Also, SQL Server 2012 is 100% backwards compatible with 2008 R2. So Express 2012 would definitely work (Microsoft is legendary for their backwards compatibility. Just sayin'.)
What kind of business are you running 200 Macs for anyway?