Hi, welcome to WCG's forums.

Yes and no. It's involved. Requires a hosting client that has internet connection [of course] and second install if that host already has BOINC running, for instance on a USB memory stick [stop regular client, start 2nd client from memory stick]. Look for Sneakernet procedures to find more expansion on the matter.

edit: Theoretically it can be done [on Windows **] by manipulating the cc_config.xml file with the options line:

<data_dir>C:\programdata\BOINC</data_dir>

When wanting to have the sneakernetted install loaded, stop BOINC, edit the path, assuming the memory stick is seen as E: to

<data_dir>E:\programdata\BOINC</data_dir>

Start BOINC, update, Stop BOINC and reverse path edit etc.

Then take memory stick and copy the files to your non-internet computer and start BOINC on that one.

Stopping BOINC is important anytime you decide to take a copy and update and alternate the active data directory on the host [internet connected] machine.

** Can be done on Linux too, but is even more involved, not enough to edit the cc_config.xml