You can always just put the 7zip archive inside of the gzip BOINC archive. It doesn't really matter what BOINC uses so long as your app just adds an extra stage to decompress the 7zip archive and compress the results before it gets packaged and sent back to BOINC. I would bet that a lot of people refuse to get on this project because of the large bandwidth requirement. There are quite a lot of people with nice computers but live in an area with bandwidth caps.

It could be a licensing issue not sure of the license it uses. You might try discussing on the BOINC message boards.

Thanks,
armstrdj

Those charts are interesting reading. From looking at them it's not difficult to see why gz is probably preferred by those running boinc projects. Low memory use and fast compress/decompress times.

Whilst from our POV .gz may be less desirable due to the larger file sizes, at the far end where the servers are the additional memory and processor load on them from compressing and decompressing millions of WU's would probably rule out most other compression methods.

I have no doubt IBM could scale up its systems to cope, but unfortunately there are many other projects running on BOINC and I suspect many of those are run on a shoestring budget and would not have the resources to beef up their servers to handle other types of compression. I think .gz will be the standard for BOINC for quite a while.