Can UltraVNC be used commercially?

Question

System administration

Greetings, comrades. Tell me, as part of my work for an Internet provider, I thought about the possibility of deploying this software on end client computers. Clients - individual entrepreneurs and LLCs, served in an official way, this integration, if desired, can be implemented under an additional agreement for technical support. The question is whether the software will be paid, and if so, where to see the prices, since I did not find it on their website.

Answer 1

GNU General Public License version 2.0 (GPLv2)
https://sourceforge.net/projects/ultravnc/

Answer 2

Can!
This is under the GPL license, and there is only a restriction that if you modify the software, then you need to share your improvements.
However, in practice it often happens (and this is the norm, as Malysheva says :-) that an organization (or an individual) changes the code, and simply uses the resulting product without posting the source code. So it's not forbidden. It is forbidden to DISTRIBUTE fixed binaries without providing source codes.
So at work we finalized one of the versions (now considered obsolete, but it was enough for our tasks), fixed almost all glitches and bugs, added an address book and other goodies - and is still in use, for many years.