It's probably me doing something wrong as honestly I have no idea but I cannot get it to run at all=S
From your instructions, i'm assuming the DemoGame.app should run as is? Then to try other games I need to put their files in the resources folder of EngineMac, renaming the exe as you've described.
Trying to run either gives me an error like: "DemoGame cannot be opened because of a problem. Check with the Developer to make sure DemoGame works with this version of Mac OS X."
The error log is as follows. Hope it helps.
Process: EngineMac [1126]
Path: /Users/USER/Downloads/*/DemoGame.app/Contents/MacOS/EngineMac
Identifier: BlueCup.EngineMac
Version: 1.0 (1)
Code Type: X86 (Native)
Parent Process: launchd [231]
Date/Time: 2012-04-09 13:18:43.432 +0100
OS Version: Mac OS X 10.7.3 (11D50)
Report Version: 9
Interval Since Last Report: 404045 sec
Crashes Since Last Report: 27
Per-App Crashes Since Last Report: 7
Anonymous UUID: F84AA333-6BA6-4384-9527-55C60A7604D5
Crashed Thread: 0
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Application Specific Information:
dyld: launch, loading dependent libraries
Dyld Error Message:
Library not loaded: @rpath/SDL.framework/Versions/A/SDL
Referenced from: /Users/USER/Downloads/*/DemoGame.app/Contents/MacOS/EngineMac
Reason: image not found
Binary Images:
0x1000 - 0x102fff +BlueCup.EngineMac (1.0 - 1) <129EB5BC-5478-3E02-BB35-2E0D9828BE14> /Users/USER/Downloads/*/DemoGame.app/Contents/MacOS/EngineMac
0x8fe8c000 - 0x8febeaa7 dyld (195.6 - ???) <3A866A34-4CDD-35A4-B26E-F145B05F3644> /usr/lib/dyld
0x9b4c0000 - 0x9b4c0fff com.apple.Cocoa (6.6 - ???) <5FAFE73E-6AF5-3D09-9191-0BDC8C6875CB> /System/Library/Frameworks/Cocoa.framework/Versions/A/Cocoa
Model: iMac5,1, BootROM IM51.0090.B09, 2 processors, Intel Core 2 Duo, 2 GHz, 4 GB, SMC 1.8f2
Graphics: ATI Radeon X1600, ATY,RadeonX1600, PCIe, 128 MB
Memory Module: BANK 0/DIMM0, 2 GB, DDR2 SDRAM, 667 MHz, 0x7F98000000000000, 0x202020202020202020202020202020202020
Memory Module: BANK 1/DIMM1, 2 GB, DDR2 SDRAM, 667 MHz, 0x7F98000000000000, 0x202020202020202020202020202020202020
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x87), Broadcom BCM43xx 1.0 (5.10.131.36.11)
Bluetooth: Version 4.0.3f12, 2 service, 18 devices, 1 incoming serial ports
Network Service: AirPort, AirPort, en1
Serial ATA Device: WDC WD1600AAJS-55M0A0, 160.04 GB
Parallel ATA Device: MATSHITADVD-R UJ-85J
USB Device: Ext HDD 1021, 0x1058 (Western Digital Technologies, Inc.), 0x1021, 0xfd100000 / 6
USB Device: Built-in iSight, apple_vendor_id, 0x8501, 0xfd400000 / 5
USB Device: Keyboard Hub, apple_vendor_id, 0x1006, 0xfd300000 / 2
USB Device: Apple Optical USB Mouse, apple_vendor_id, 0x0304, 0xfd330000 / 4
USB Device: Apple Keyboard, apple_vendor_id, 0x0250, 0xfd320000 / 3
USB Device: Bluetooth USB Host Controller, apple_vendor_id, 0x8206, 0x7d100000 / 2
USB Device: IR Receiver, apple_vendor_id, 0x8240, 0x7d200000 / 3