I had an inquiry from a GIMP user to see if my templates would work in GIMP. As I don’t have the program myself and haven’t heard from anyone about this before, I quickly put a test layered template together with a locked background layer, a grey box layer, and a text layer and sent it to her to try out – and I sent it over in both PSD and TIF file versions. She reported back that the test template works perfectly – and she is able to open the layered PSD file in GIMP and then needs to save it as an XCF file – the GIMP file extension, but says it works perfectly for her.
GIMP is a free source software that is used as an alternative to Photoshop, PSE and PSP. Again, I have never used it and I don’t know what its limitations are, strengths, weaknesses, etc. but it appears to work on both Windows and Mac platforms among others and you can read more about it here.