RS wrote:

Compared to the command-line SETI, is the new BOINC generally well behaved
.... not using CPU cycles when other programs need attention ?

Boinc starts the science apps with a lower priority per default.
If you launch a application which needs CPU, the scheduler of the OS reduces the CPU cycles for the science app, and give your application the CPU.

The classic starts with normal priority, if you not configure anything else.

Lars