You have a late 2008 MacBook Unibody (aluminum) aka MacBook5,1?
Your second link is pointing to an article about a different model.
According to Apple your computer supports up to 4GB ram (total), but people are running successfully up to 8GB.
Reputable RAM vendor such as OWC offers 8GB kit for your MacBook, however you should upgrade your EFI (quote from OWC):
How to you ensure your MacBook/MacBook Pro can address 8GB of RAM
Check the Boot ROM Version in your System Profiler at this link:
MacBook Pros with a Model ID of MacBookPro5,1 should have a Boot ROM Version of MBP51.007E.B05.
MacBooks with a Model ID of MacBook5,1 should have a Boot ROM version of MB51.007D.B03
Machines with other Model IDs are not affected and don't need an update.
If your Boot ROM version does not match the numbers above, download the appropriate
For MacBook Pros (MacBookPro5,1)
MacBook Pro EFI Firmware Update 1.8 (Apple.com Download)
For MacBooks (MacBook5,1)
MacBook EFI Firmware Update 1.4 (Apple.com Download)
Once you have ensured that the Boot ROM is the correct version,
make sure your Operating System is updated to Mac OS X v10.6.6.
You must be running Snow Leopard to address 8GB on these systems.
Once you upgrade your EFI, you should be fine.