VOTE: plantuml. Thanks !
PlantUML is free software. The code is Open Source and the tool is free to use.
PlantUML is open to the community. Feedbacks, suggestions, ideas, codes, plugins coming... from the community are a great part in the success of PlantUML.
However, developing and hosting PlantUML take time. Some users have already made donation to help us, and again we thank them for that.
Since this was not sufficient, we have to use ads to be able to survive in the real world.
Another option that we are considering now is to use some crowdfunding. We do not want to get a large funding in one shot, we would like better to obtain funding from patrons on a recurring basis.
That's why we decide to go to Patreon.
We decide to go for 1€ or 1$ per month. This may sound quite low to you, but if hundreds of people apply to a subscription, it will mean a lot to us.
And to show you that we are serious here, we will give to ours patrons an access to an ad-free version of the current website.