How to make the difference : Examine the licensing terms:
In theory, it's quite easy : see the table bellow.
In practice, consult the experts.
Basic picture :
Table 1. Rights granted
Proprietary software | FLOSS | |
---|---|---|
Right to use : | Yes (but limited) | Yes |
Right to study : | No | Yes |
Right to modify : | No | Yes |
Right to copy : | No | Yes |
Sometimes, vendors tend to invent complicated licenses, and it becomes hard to interpret the licensing terms.
So rather trust experts : Free Software Foundation (http://www.fsf.org/), OpenSource initiative (http://www.opensource.org/).