OSS

1. Short for Open-Source Software, OSS is a type of software source code that is freely distributed to help develop the software and/or allow for customization with the software. Perl is a good example of an OSS software program. Unlike freeware Open-Source software allows any user to modify the code.
2. Short for Operations Support Systems, OSS are automated systems developed by the telecommunications industry to assist customers with various services, such as billing and maintenance. 

Also see: Freeware, GNU, Open source, Perl, Software