Announcing Jumpgate: Our Modern Overhaul of the Roll20 VTT - Roll20 Blog

Rolisteam is a FOSS VTT.

Let's be honest, it was very great in 2010, before roll20, when the alternative where either Super-heavy maptool, and expensive fantasy ground, but the project hasn't evolved much since then. But it does what you expect from a VTT including

• Shared white-boards, with or without grid and background image (aka map), on which you can draw, and put tokens
• Roll dice with any possible way
• Group text chat, and private text-chat
• Shared notes
• Shared character sheets

It's definitely less modern than stuff like roll20 or let's role, but it's still doing the job even though it hasn't evolved much in 10 years. Also it's a FOSS project using Qt and C++ , so I am sure that if someone wants to contributes it's possible