Is there a good and simple Teamviewer alternative?

Question

Presentations

We very often used Teamviewer during meetings (dedicated employees) and with clients, but now it has a limit of 5 minutes after which it is cut off for 2 minutes (does not allow to connect). They even wanted to buy it, but it costs some unrealistic money.
Is there an alternative and who uses what?
And maybe someone knows how to simultaneously show the contents of my desktop to two or more people (not skype, it's buggy)?

Answer 1

Successfully used OpenSource VNC and OpenVPN (you need one public IP address on the OpenVPN server): cross-platform, and do not put yourself dangerous potential trojans, do not depend on anyone.
And yet, you can get, if necessary, access at the L2 level to another network: this will not give any teamviewer. You can, for example, do Wake-on-Lan through the router on which you installed OpenVPN.
And the sound can be put through Skype or phone.