The Linux apps use legacy vsyscall which is disabled by default in a lot of distributions for security reasons. Work units run anywhere from a few seconds to days. Earning credit seems to be like playing the lottery...CPU time of 1,000 seconds and earn 3,000 credit or CPU time of 800,000 seconds and earn 100 credit. Check pointing is also hit or miss. Not a big fan of running this project.
I didn't remember those particulars but I never cared for it either. This is what I settled on for my systems when I was crunching it.
If I recall correctly the better credit was with the small composites even though they don't run very long, but they can be hard to get.