Sourcerer doesn't work exactly the same as Jumi. Jumi is aimed mainly at including external files. Sourcer aimed mainly at placing inline code. You can include external php files too with Sourcerer. But it doesn't have a menu to select available php files. You are free to include any (php) file you want:
www.nonumber.nl/forum/14-sourcerer/5172-...o-include-a-php-file
Regarding the admin code. Still same answer.
You can select in the plugins security settings in which areas Sourcerer should be active.