GNU General Public License, version 3
For you, the users of Radinus:
Under the GNU GPL v3 licence, Radinus guarantees you four fundamental freedoms: to use the software as you see fit and for any purpose, including professional use; to study how it works, thanks to the published source code; to modify it to suit your needs; and to pass it on to others. There is no time limit, no cap on the number of machines, and no feature held back for a paid edition. What sets this apart from a permissive licence is one further guarantee: any modified version of Radinus that is redistributed must be released under the same licence, together with its source code. In other words, nobody can take Radinus and turn it into closed or paid-for software. The freedom you enjoy today is protected for tomorrow.
For you, the developers:
The Radinus code is entirely open to you: you may read it, run it, fix it, fork it and reuse its mechanisms in your own work. The condition fits in a single sentence: if you distribute software derived from Radinus, you must distribute it under the GPL v3 licence and provide its source code, keeping the copyright and licence notices intact. That reciprocity is what is known as copyleft: it ensures that improvements made by one benefit all. Version 3 adds two protections that version 2 lacked: an explicit patent licence, which shields contributors and users from action by those who distribute the code, and the anti-tivoisation clause, which forbids shipping the software on locked-down hardware where the user cannot install their own modified version.