Qdeathstar:
start charging for the IDE.
I don't think that would be possible without a complete rewrite since it is all open source. They can charge for the download or to sell CDs with the IDE on them but anyone else could just set up a torrent so I doubt many people would pay. I think it would be less profitable than the current request for donations. That even fools some people into thinking they have to pay to download because the "Just Download" button is less prominent. If they went closed source you would see an immediate fork and most of the contributors would abandon Arduino and work on the open fork instead. I know I wouldn't have gotten involved with Arduino if it wasn't all based on open source. There are other options.
They did make as much of the Arduino Web Editor as they could closed source and they're even charging $0.99/mo for the Chrome app version. But that means most of the work on the project has to be done by paid employees. I was offered to be a tester but I would rather spend my time working on open source projects so I didn't do it. I don't necessarily fault them for the decision, I'm sure there were good reasons.