(b)Cost sharing arrangement. A cost sharing arrangement is an arrangement by which controlled participants share the costs and risks of developing cost shared intangibles in proportion to their RAB shares. An arrangement is a CSA if and only if the requirements of paragraphs (b)(1) through (4) of this section are met.
Asterisk is a complete PBX in software. It runs on Linux, BSD, Windows (emulated) and OS X and provides all of the features you would expect from a PBX and more. Asterisk does voice over IP in four protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.
Note: Normally an asterisk (*) means 0 or more of the previous thing but in the example above, it does not have that meaning, since the asterisk is inside of the character class, so it loses its special-ness. For more information on regular expressions in Python, the two official references are the re module, the Regular Expression HOWTO.