This is actually a recommendation, but there is no "Suggestions for BAM!" forum...

I was just looking at the More Site Statistics page, and I was shocked by how many different versions of the client are being used out there. I was also bothered by how very few of them (just 2.4%!) are actually the current version (currently 7.4.42), but a bit relieved that 7.4.36 (only 3 months old) is at 17.1%. The most used one is 7.2.42, from Feb'14, used by more than a quarter of the BAM! attached hosts. Of course, that is the recommended version for some Mac OS X and most Linux, according to http://boinc.berkeley.edu/download_all.php. So, assuming BAM! knows the OS version of each host, and could have an internal database table of [OS version,latest client version] pairings, then...

First, it should show that OS info in the table on Host List for each host, as well as a column with the version number of the latest client applicable to that OS, right next to the already existing Client Version cell.

Then, somewhere on that page should be a bit of text telling people that the latest BOINC clients are available on http://boinc.berkeley.edu/download.php. Extra text in there could also tell them how many out of date hosts out of how many hosts they have, along with a percentage representation of that ratio. Extra points if the non-current client version numbers in the list could have a different background or font color, like red, and have a tooltip pop up telling the user that this client is out of date.

Yup, basically show the user what is old in a way they cannot not see, and give them everything they need to update them.

And, I just saw the Download BOINC page. So, BS already has the [OS vs. BOINC] version data, making what I described below doable.