- Can I charge the customer for software? This includes selling the software as well as charging for technical support?
Yes, GPL v3 is a free software licence, and you are always allowed to do these things with free (as in freedom) software. In fact, GPL v3 section 4 explicitly covers both of these issues:
You may charge any price … for each copy that you convey, and you may offer support … for a fee.
Back to the question:
- If the software is known by name 'ABC', can I change the name of software to 'xyz'.This may include changing the logo, name on the UI?
Yes, you are always allowed to do this with free software. However, this produces a derivative work, and some licences, including GPL v3, have special rules for derivative works. GPL v3 section 5 covers derivative works; in summary, you must:
- Add notices about the changes.
- Release your modified version under GPL v3 (or AGPL v3 – see section 13).
- Ensure that interactive user interfaces display the appropriate notices.
- Do I need to provide the copy of source code voluntarily? I am fine to provide the source code if some body asks for it.
GPL v3 section 6 covers this. In summary, when you convey object code, you must either include a copy of the source code or information about how to obtain the source code. The details depend on how you convey the object code and whether the distribution is commercial.
- Is it necessary to publish the modified source code if I host it in the cloud?
No, GPL v3 never requires publishing source code. The most you might need to do is, when you convey the object code to someone, convey the source code as well.
Also watch out for the similar licence AGPL (Affero General Public Licence), which was designed specifically for this situation. That licence would require you to make the modified source code available to users in this situation.