As I write this, I have
this host crunching a CPDN work unit, with the 64bit BOINC client installed.
After I did a lot of searching in order to find an easy solution to get my 64bit Boinc client accepted by the CPDN server, I decided that I had to "fool" the server, by intercepting the client request and change it on-the-fly, replacing the 64bit fingerprint with the 32bit one.
I used a php script (which I found ready from onlamp.com) that acts as a proxy server (it opens a socket in a single thread) and a free proxy server for windows.
Then I configured the proxy server to forward all request directed to the scheduler of CPDN, to the php proxy server script.
In that script, I intercept the POST request, replace the 64bit platform string with the 32bit, re-calculate the content-length (so that it evaluates to the CPDN serrver) and send it to the CPDN scheduler.
Then the script receives the response from CPDN and forwards it to the Boinc client.
That was just a proof of concept and I'm going to work this weekend on a complete program for windows so that it can be configured to change a platform string, only for the projects that needs it.
If I read correctly, the 64bit Boinc client on Linux, can run 32bit applcations, as long as it has all necessary 32bit dependencies installed.
If that's the case, then it should be safe to apply the same principle for Linux also (I can create a perl script for that)
Feel free to share your comments, ideas, etc